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The following Test is based on the syllabus of 60 Days Plan-2023 for UPSC IAS Prelims 2022.
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Consider the following statements:
Which of the statements given above is/are correct?
Solution (b)
| Statement 1 | Statement 2 |
| Incorrect | Correct |
| Ecosystem: All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem | An ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals. |
Solution (b)
| Statement 1 | Statement 2 |
| Incorrect | Correct |
| Ecosystem: All organisms such as plants, animals, microorganisms and human beings as well as the physical surroundings interact with each other and maintain a balance in nature. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem | An ecosystem consists of biotic components comprising living organisms and abiotic components comprising physical factors like temperature, rainfall, wind, soil and minerals. |
Consider the following statements regarding Food Chain:
How many of the above statements are correct?
Solution (b)
| Statement 1 | Statement 2 | Statement 3 |
| Correct | Incorrect | Correct |
| Food chain is a series of organisms taking part in feeding at various biotic levels. Each step or level of the food chain forms a trophic level. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers. The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level. | There is a loss of energy as we go from one trophic level to the next, this limits the number of trophic levels in a food-chain. Thus, food chains generally consist of only three or four levels. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. | The flow of energy in food chain in unidirectional because the sun is the only source of energy for all ecosystems on earth. Then the energy is captured by the autotrophs does not revert back to the sun. Therefore, in the food chain, the energy moves progressively through various trophic levels. |
Solution (b)
| Statement 1 | Statement 2 | Statement 3 |
| Correct | Incorrect | Correct |
| Food chain is a series of organisms taking part in feeding at various biotic levels. Each step or level of the food chain forms a trophic level. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or the consumers. The herbivores or the primary consumers come at the second, small carnivores or the secondary consumers at the third and larger carnivores or the tertiary consumers form the fourth trophic level. | There is a loss of energy as we go from one trophic level to the next, this limits the number of trophic levels in a food-chain. Thus, food chains generally consist of only three or four levels. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. | The flow of energy in food chain in unidirectional because the sun is the only source of energy for all ecosystems on earth. Then the energy is captured by the autotrophs does not revert back to the sun. Therefore, in the food chain, the energy moves progressively through various trophic levels. |
‘Ten Percent Law’ is associated with which of the following?
Solution (a)
Ten per cent law was given by Lindeman which states that only 10% of energy contained in a lower trophic level is available to next higher tropic level, the remaining 90% being lost as heat to the environment, into digestion and in doing work and the rest goes towards growth and reproduction. Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.
Solution (a)
Ten per cent law was given by Lindeman which states that only 10% of energy contained in a lower trophic level is available to next higher tropic level, the remaining 90% being lost as heat to the environment, into digestion and in doing work and the rest goes towards growth and reproduction. Therefore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of consumers.
Which of the given term describes not only the physical space occupied by an organism but also its functional role in the community of organisms?
Solution (b)
Ecological niche can be defined as the functional role and position (micro-habitat) of species in its ecosystem, including what resources it uses, how and when it uses the resources, and how it interacts with other species.
Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.
Solution (b)
Ecological niche can be defined as the functional role and position (micro-habitat) of species in its ecosystem, including what resources it uses, how and when it uses the resources, and how it interacts with other species.
Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.
Consider the following statements regarding Homeostasis:
Which of the statements given above is/are correct?
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Homeostasis refers to maintenance of a constant internal environment by the organisms. This contributes to optimal performance of organisms | In a homeostatic system, negative feedback mechanism is responsible for maintaining stability in an ecosystem.
Only some organisms (regulators) are capable of homeostasis in the face of changing external environment. Others either partially regulate their internal environment or simply conform. |
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Homeostasis refers to maintenance of a constant internal environment by the organisms. This contributes to optimal performance of organisms | In a homeostatic system, negative feedback mechanism is responsible for maintaining stability in an ecosystem.
Only some organisms (regulators) are capable of homeostasis in the face of changing external environment. Others either partially regulate their internal environment or simply conform. |
What is the meaning of term ‘Diapause’?
Solution (c)
Diapause is the ability of an organism to suspend its development owing to extreme environmental conditions. In this state, developmental arrest or dormancy is seen that signifies shutting down of most life processes. This kind of physiological state is found mostly in arthropods. During the life cycle of an insect, diapause can happen at any stage such as embryonic, larval, pupal, and adult. This developmental arrest is a spontaneous response amongst these animals to survive unfavourable environmental conditions.
Solution (c)
Diapause is the ability of an organism to suspend its development owing to extreme environmental conditions. In this state, developmental arrest or dormancy is seen that signifies shutting down of most life processes. This kind of physiological state is found mostly in arthropods. During the life cycle of an insect, diapause can happen at any stage such as embryonic, larval, pupal, and adult. This developmental arrest is a spontaneous response amongst these animals to survive unfavourable environmental conditions.
“Mammals from colder climates generally have shorter ears and limbs to minimise heat loss”, This rule is known as?
Solution (b)
Allen’s Rule says that mammals from colder climates generally have shorter ears and limbs to minimise heat loss. In the polar seas aquatic mammals like seals have a thick layer of fat (blubber) below their skin that acts as an insulator and reduces loss of body heat.
Bergmann’s rule says that animals or organisms residing at a higher altitude should be larger and have a thicker coat than those that are living at lower altitudes and found close to the equator.
Solution (b)
Allen’s Rule says that mammals from colder climates generally have shorter ears and limbs to minimise heat loss. In the polar seas aquatic mammals like seals have a thick layer of fat (blubber) below their skin that acts as an insulator and reduces loss of body heat.
Bergmann’s rule says that animals or organisms residing at a higher altitude should be larger and have a thicker coat than those that are living at lower altitudes and found close to the equator.
Consider the following statements regarding ‘Insectivorous Plants’:
Which of the statements given above is/are correct?
Solution (b)
| Statement 1 | Statement 2 |
| Incorrect | Correct |
| Insectivorous plants are a specialized group of plants that grow in wet, acidic soils.
|
· One of the most critical plant nutrients is nitrogen which is usually taken up by plants as nitrates. Nitrogen is a nutrient that is easily leached out of soils.
· For this reason, the plants that live in these soils have evolved into carnivorous plants that capture and digest insects as a means of obtaining nitrates. These plants are usually associated with leached, nutrient-poor soils, or wet and acidic areas that are ill-drained.
|
Solution (b)
| Statement 1 | Statement 2 |
| Incorrect | Correct |
| Insectivorous plants are a specialized group of plants that grow in wet, acidic soils.
|
· One of the most critical plant nutrients is nitrogen which is usually taken up by plants as nitrates. Nitrogen is a nutrient that is easily leached out of soils.
· For this reason, the plants that live in these soils have evolved into carnivorous plants that capture and digest insects as a means of obtaining nitrates. These plants are usually associated with leached, nutrient-poor soils, or wet and acidic areas that are ill-drained.
|
Which of the following statement is correct?
Solution (b)
The important steps in the process of decomposition are: fragmentation, leaching, catabolism, humification and mineralisation.
Solution (b)
The important steps in the process of decomposition are: fragmentation, leaching, catabolism, humification and mineralisation.
Consider the following statements regarding Decomposition:
Which of the statements given above is/are correct?
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Decomposition is largely an oxygen-requiring process. The rate of decomposition is controlled by chemical composition of detritus and climatic factors. | In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars. Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in buildup of organic materials. |
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Decomposition is largely an oxygen-requiring process. The rate of decomposition is controlled by chemical composition of detritus and climatic factors. | In a particular climatic condition, decomposition rate is slower if detritus is rich in lignin and chitin, and quicker, if detritus is rich in nitrogen and water-soluble substances like sugars. Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in buildup of organic materials. |
Consider the following statements:
Select the correct answer using the code given below:
Solution (d)
| Statement 1 | Statement 2 |
| Incorrect | Incorrect |
| In an aquatic ecosystem, the grazing food chain (GFC) is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain (DFC) than through the GFC. | Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web. |
Solution (d)
| Statement 1 | Statement 2 |
| Incorrect | Incorrect |
| In an aquatic ecosystem, the grazing food chain (GFC) is the major conduit for energy flow. As against this, in a terrestrial ecosystem, a much larger fraction of energy flows through the detritus food chain (DFC) than through the GFC. | Detritus food chain may be connected with the grazing food chain at some levels: some of the organisms of DFC are prey to the GFC animals, and in a natural ecosystem, some animals like cockroaches, crows, etc., are omnivores. These natural interconnection of food chains make it a food web. |
Consider the following pairs
How many of the above pairs are correctly matched?
Solution (b)
| Statement 1 | Statement 2 | Statement 3 | Statement 4 |
| Correct | Incorrect | Incorrect | Correct |
| Certain organisms are capable of fixing atmospheric nitrogen into ammonium ions. These include free living nitrifying bacteria (e.g. aerobic Azotobacter and anaerobic Clostridium) and
symbiotic nitrifying bacteria living in association with leguminous plants and symbiotic bacteria living in non-leguminous root nodule plants (e.g. Rhizobium) as well as blue green algae (e.g. Anabaena, Spirulina). |
Ammonium ions can be directly taken up as a source of nitrogen by some plants, or are oxidized to nitrites or nitrates by two groups of specialized bacteria: Nitrosomonas bacteria promote transformation of ammonia into nitrite. | Nitrite is then further transformed into nitrate by the Nitrobacter bacteria. | In the soil as well as oceans there are special denitrifying bacteria (e.g. Pseudomonas), which convert the nitrates/nitrites to elemental nitrogen |
Solution (b)
| Statement 1 | Statement 2 | Statement 3 | Statement 4 |
| Correct | Incorrect | Incorrect | Correct |
| Certain organisms are capable of fixing atmospheric nitrogen into ammonium ions. These include free living nitrifying bacteria (e.g. aerobic Azotobacter and anaerobic Clostridium) and
symbiotic nitrifying bacteria living in association with leguminous plants and symbiotic bacteria living in non-leguminous root nodule plants (e.g. Rhizobium) as well as blue green algae (e.g. Anabaena, Spirulina). |
Ammonium ions can be directly taken up as a source of nitrogen by some plants, or are oxidized to nitrites or nitrates by two groups of specialized bacteria: Nitrosomonas bacteria promote transformation of ammonia into nitrite. | Nitrite is then further transformed into nitrate by the Nitrobacter bacteria. | In the soil as well as oceans there are special denitrifying bacteria (e.g. Pseudomonas), which convert the nitrates/nitrites to elemental nitrogen |
Consider the following statements regarding ‘Ecosystem Services’:
How many of the above statements are correct?
Solution (c)

Solution (c)

Consider the following statements
Which of the statements given above is/are correct?
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| With respect to earth’s biodiversity, More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. | Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. |
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| With respect to earth’s biodiversity, More than 70 per cent of all the species recorded are animals, while plants (including algae, fungi, bryophytes, gymnosperms and angiosperms) comprise no more than 22 per cent of the total. | Among animals, insects are the most species-rich taxonomic group, making up more than 70 per cent of the total. |
Which of the following countries is not a Mega diversity country?
Solution (c)
The 17 Mega-diverse countries are:
Solution (c)
The 17 Mega-diverse countries are:
Consider the following statements:
Select the correct answer using the code given below:
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Latitudinal gradients: The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. For many group of animals or plants, there are interesting patterns in diversity, the most well- known being the latitudinal gradient in diversity. In general, species diversity decreases as we move away from the equator towards the poles. | Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity. There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity |
Solution (a)
| Statement 1 | Statement 2 |
| Correct | Incorrect |
| Latitudinal gradients: The diversity of plants and animals is not uniform throughout the world but shows a rather uneven distribution. For many group of animals or plants, there are interesting patterns in diversity, the most well- known being the latitudinal gradient in diversity. In general, species diversity decreases as we move away from the equator towards the poles. | Speciation is generally a function of time, unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.
Tropical environments, unlike temperate ones, are less seasonal, relatively more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity. There is more solar energy available in the tropics, which contributes to higher productivity; this in turn might contribute indirectly to greater diversity |
Consider the following statements:
Which of the above statements are features of stable community?
Solution (b)
A Stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
Solution (b)
A Stable community should not show too much variation in productivity from year to year; it must be either resistant or resilient to occasional disturbances (natural or man-made), and it must also be resistant to invasions by alien species.
It is an area of uniform environmental conditions providing a living place for a specific assemblage of plants and animals. Which of the following term is being referred to here?
Solution (b)
Solution (b)
Consider the following statements:
Which of the above add carbon dioxide to the carbon cycle on Earth?
Solution (d)
| 1. | 2. | 3. | 4. |
| Consumption of Fossil Fuels | Microbial Respiration in Oceans | Zooplankton Grazing in Oceans | Auto and Factory emissions |
| Correct | Correct | Correct | Correct |
| Consumption of Fossil Fuels adds CO2 from the carbon cycle. | Microbial Respiration in Oceans adds CO2 to the carbon cycle on Earth. | Zooplankton Grazing in Oceans adds CO2 to the carbon cycle on Earth. | Auto and Factory emissions adds CO2 to the carbon cycle on Earth. |
Notes:
Carbon cycle-
Solution (d)
| 1. | 2. | 3. | 4. |
| Consumption of Fossil Fuels | Microbial Respiration in Oceans | Zooplankton Grazing in Oceans | Auto and Factory emissions |
| Correct | Correct | Correct | Correct |
| Consumption of Fossil Fuels adds CO2 from the carbon cycle. | Microbial Respiration in Oceans adds CO2 to the carbon cycle on Earth. | Zooplankton Grazing in Oceans adds CO2 to the carbon cycle on Earth. | Auto and Factory emissions adds CO2 to the carbon cycle on Earth. |
Notes:
Carbon cycle-
With reference to ‘Carrying Capacity’ of an environment, consider the following statements:
Which of the statements given above is/are correct?
Solution (c)
| Statement 1 | Statement 2 |
| Correct | Correct |
| It is the maximum population size of biological species that can be sustained in that specific environment. | The carrying capacity is different for each species in a given habitat. |
Notes:
The carrying capacity of an environment is the maximum population size of a biological species that can be sustained in that specific environment, given the food, habitat, water, and other resources available.
The carrying capacity is different for each species in a habitat because of that species’ particular food, shelter, and social requirements. Disease, competition, predator-prey interaction, resource use and the number of populations in an ecosystem all affect carrying capacity. It does not relate to the diversity of species. Important direct drivers affecting biodiversity are habitat change, climate change, invasive species, overexploitation, and pollution.
Populations grow through births and immigration and decline through deaths and emigration. When resources are unlimited, the growth is usually exponential but when resources become progressively limiting, the growth pattern turns logistic. The intrinsic rate of natural increase (r) is a measure of the inherent potential of a population to grow. The ‘intrinsic rate of natural increase’ is a very important parameter chosen for assessing impacts of any biotic or abiotic factor on population growth.
Solution (c)
| Statement 1 | Statement 2 |
| Correct | Correct |
| It is the maximum population size of biological species that can be sustained in that specific environment. | The carrying capacity is different for each species in a given habitat. |
Notes:
The carrying capacity of an environment is the maximum population size of a biological species that can be sustained in that specific environment, given the food, habitat, water, and other resources available.
The carrying capacity is different for each species in a habitat because of that species’ particular food, shelter, and social requirements. Disease, competition, predator-prey interaction, resource use and the number of populations in an ecosystem all affect carrying capacity. It does not relate to the diversity of species. Important direct drivers affecting biodiversity are habitat change, climate change, invasive species, overexploitation, and pollution.
Populations grow through births and immigration and decline through deaths and emigration. When resources are unlimited, the growth is usually exponential but when resources become progressively limiting, the growth pattern turns logistic. The intrinsic rate of natural increase (r) is a measure of the inherent potential of a population to grow. The ‘intrinsic rate of natural increase’ is a very important parameter chosen for assessing impacts of any biotic or abiotic factor on population growth.
Consider the following statements:
How many of the above statements are correct?
Solution (c)
Kerch Strait connects the Black Sea to the Sea of Azov. Hence statement 3 is correct.
Solution (c)
Kerch Strait connects the Black Sea to the Sea of Azov. Hence statement 3 is correct.
Consider the following statements about the Index of Industrial Production (IIP):
How many of the above statements are correct?
Solution (b)
Solution (b)
Consider the following statements about Gharials:
How many of the above statements are correct?
Solution (c)
Solution (c)
Consider the following statements regarding Rudragiri Hillock:
How many of the above statements are correct?
Solution (b)
Note:
Kakatiya kingdom was a south Indian dynasty that ruled most of the eastern Deccan region comprising present-day Telangana and Andhra Pradesh, and parts of eastern Karnataka and southern Odisha. They ruled between the 12th and 14th centuries.
Solution (b)
Note:
Kakatiya kingdom was a south Indian dynasty that ruled most of the eastern Deccan region comprising present-day Telangana and Andhra Pradesh, and parts of eastern Karnataka and southern Odisha. They ruled between the 12th and 14th centuries.
Consider the following statements about PM SVANidhi Scheme:
How many of the above statements are correct?
Solution (b)
Solution (b)
Consider the following statements about picolinic acid:
How many of the above statements are correct?
Solution (c)
Solution (c)
Which of the following activities are eligible for benefits under the Animal Husbandry Infrastructure Development Fund (AHIDF)?
Choose the correct code:
Solution (d)
Animal Husbandry Infrastructure Development Fund (AHIDF) was launched in 2021 by the Ministry of Fisheries, Animal Husbandry and Dairying. It is implemented by the Department of Animal Husbandry & Dairying. Its objectives are:
The activities are eligible for benefits under the Animal Husbandry Infrastructure Development Fund (AHIDF) are:
Hence, option d is correct.
Solution (d)
Animal Husbandry Infrastructure Development Fund (AHIDF) was launched in 2021 by the Ministry of Fisheries, Animal Husbandry and Dairying. It is implemented by the Department of Animal Husbandry & Dairying. Its objectives are:
The activities are eligible for benefits under the Animal Husbandry Infrastructure Development Fund (AHIDF) are:
Hence, option d is correct.
Consider the following statements about Bacteriophages:
How many of the above statements are correct?
Solution (b)
Solution (b)
Consider the following statements about DPT3 Vaccine:
How many of the above statements are correct?
Solution (b)
Solution (b)
Consider the following statements:
How many of the above statements are correct?
Solution (b)
Solution (b)
The product of all integers from 1 to 200 will have the following numbers of zeros at the end:
Solution (b)
Method I
The product of all integers from 1 to 200 = 200!
In case of ‘n!’ (n = a natural number): (number of 2’s) ≥ (number of 5’s).
The number of zeros at the end = Lowest of the (number of 2’s, number of 5’s) = Number of 5’s.
[As 10 = 2× 5, so one 2 and one 5 is needed for a zero at the end].
So, we have to find only number of 5’s in ‘n!’.
Calculation of number of 5’s in ‘200!’:
Step 1: 200/5 = 40
Step 2: 40/5 = 8
Step 3: 8/5 = 1 (ignore the fractional part)
Total number of 5’s in ‘200!’ = 40 + 8 + 1 = 49.
Method ІІ
Number of 2’s in the product of all integers from 1 to 200 (i.e. 200!) = *200/2+ + *200/22] + [200/23] + [200/24] + [200/25] + [200/26] + [200/27] + [200/28]
([.] denotes the greatest integer; i.e. take only integral part, ignore the fractional part if the number is non – negative, e.g. [200/24] = [12.5] = 12)
= 100 + 50 + 25 + 12 + 6 + 3 + 1 + 0 = 197.
Number of 5’s in the product of all integers from 1 to 200 (i.e. 200!) = *200/5+ + *200/52] + [200/53] + [200/54] = 40 + 8 + 1 + 0 = 49.
Hence, the number of zeros at the end = Lowest of the (number of 2’s, number of 5’s) = 49.
Solution (b)
Method I
The product of all integers from 1 to 200 = 200!
In case of ‘n!’ (n = a natural number): (number of 2’s) ≥ (number of 5’s).
The number of zeros at the end = Lowest of the (number of 2’s, number of 5’s) = Number of 5’s.
[As 10 = 2× 5, so one 2 and one 5 is needed for a zero at the end].
So, we have to find only number of 5’s in ‘n!’.
Calculation of number of 5’s in ‘200!’:
Step 1: 200/5 = 40
Step 2: 40/5 = 8
Step 3: 8/5 = 1 (ignore the fractional part)
Total number of 5’s in ‘200!’ = 40 + 8 + 1 = 49.
Method ІІ
Number of 2’s in the product of all integers from 1 to 200 (i.e. 200!) = *200/2+ + *200/22] + [200/23] + [200/24] + [200/25] + [200/26] + [200/27] + [200/28]
([.] denotes the greatest integer; i.e. take only integral part, ignore the fractional part if the number is non – negative, e.g. [200/24] = [12.5] = 12)
= 100 + 50 + 25 + 12 + 6 + 3 + 1 + 0 = 197.
Number of 5’s in the product of all integers from 1 to 200 (i.e. 200!) = *200/5+ + *200/52] + [200/53] + [200/54] = 40 + 8 + 1 + 0 = 49.
Hence, the number of zeros at the end = Lowest of the (number of 2’s, number of 5’s) = 49.
A kid has been given 4 consonants and 3 vowels. How many words can the kid form with these if he has to use only 3 consonants and 2 vowels in one word?
Solution (b)
Number of ways of selecting 3 consonants from a set of 4 consonants = 4C3 = 4
Number of ways of selecting 2 vowels from a set of 3 vowels = 3C2 = 3
Number of ways of selecting 3 consonants and 2 vowels = 4 × 3 =12
So, number of ways of forming a five lettered word = 12 × 5!
Solution (b)
Number of ways of selecting 3 consonants from a set of 4 consonants = 4C3 = 4
Number of ways of selecting 2 vowels from a set of 3 vowels = 3C2 = 3
Number of ways of selecting 3 consonants and 2 vowels = 4 × 3 =12
So, number of ways of forming a five lettered word = 12 × 5!
X is the set of positive integers such that when divided by 24, 32 and 36 these integers leave the remainders 19, 27 and 31 respectively. How many integers between 1 and 1000 belong to set X?
Solution (b)
Note that the difference between the divisors and the remainders is constant.
24 – 19 = 5; 32 – 27 = 5; 36 – 31 = 5
In such a case, the required number will always be [a multiple of LCM (24, 32, 36) – (The constant difference)], i.e. [n× LCM (24, 32, 36) – 5]
(n= natural number)
Now, 24 = 23 × 3; 32 = 25; 36 = 22 × 32
So, LCM (24, 32, 36) = 25×32 = 288.
Hence, the required number = n×288 – 5
For n=1, X1 = 1 × 288 – 5 = 283
For n=2, X2 = 2 × 288 – 5 = 571
For n=3, X3 = 3 × 288 – 5 = 859.
So, between 1 and 1000, there are three such numbers, viz. 283, 571 and 859.
Solution (b)
Note that the difference between the divisors and the remainders is constant.
24 – 19 = 5; 32 – 27 = 5; 36 – 31 = 5
In such a case, the required number will always be [a multiple of LCM (24, 32, 36) – (The constant difference)], i.e. [n× LCM (24, 32, 36) – 5]
(n= natural number)
Now, 24 = 23 × 3; 32 = 25; 36 = 22 × 32
So, LCM (24, 32, 36) = 25×32 = 288.
Hence, the required number = n×288 – 5
For n=1, X1 = 1 × 288 – 5 = 283
For n=2, X2 = 2 × 288 – 5 = 571
For n=3, X3 = 3 × 288 – 5 = 859.
So, between 1 and 1000, there are three such numbers, viz. 283, 571 and 859.
A two-digit number n1 is divisible by 12, 15 and 20 and n2 is nearest perfect square to number n1. Then find n2-n1
Solution (b)
Number n1 is divisible by 12, 15 and 20 so we find its LCM of these numbers
= 2|12, 15, 20
= 2|6, 15, 10
= 3|3, 15, 5
= 5|1, 5, 5
= |1, 1, 1
So LCM of 12, 15 and 20 = 2 × 2 × 3 × 5 = 60
So lowest possible number divisible by 12, 15 and 20 = 60
So n1 = 60
Nearest perfect square near 60 = 64=n2
So n2 – n1= 64 – 60 = 4.
Solution (b)
Number n1 is divisible by 12, 15 and 20 so we find its LCM of these numbers
= 2|12, 15, 20
= 2|6, 15, 10
= 3|3, 15, 5
= 5|1, 5, 5
= |1, 1, 1
So LCM of 12, 15 and 20 = 2 × 2 × 3 × 5 = 60
So lowest possible number divisible by 12, 15 and 20 = 60
So n1 = 60
Nearest perfect square near 60 = 64=n2
So n2 – n1= 64 – 60 = 4.
Which of the following number(s) is/are not prime?
Choose the correct code:
Solution (d)
In expression (an + bn)/ (a + b), Remainder = 0, if n is odd.
[i.e. (an + bn) is divisible by (a + b) if n is an odd number].
So, (22001 + 1) and (22003 + 1) both are divisible by (2 + 1), i.e. 3.
Now, 22002 + 1 = (22)1001 + 1 = 41001 + 1, which is divisible by (4 + 1), i.e. 5.
Hence, none of the given numbers is a prime number.
Solution (d)
In expression (an + bn)/ (a + b), Remainder = 0, if n is odd.
[i.e. (an + bn) is divisible by (a + b) if n is an odd number].
So, (22001 + 1) and (22003 + 1) both are divisible by (2 + 1), i.e. 3.
Now, 22002 + 1 = (22)1001 + 1 = 41001 + 1, which is divisible by (4 + 1), i.e. 5.
Hence, none of the given numbers is a prime number.
All the Best
IASbaba