Prelims Solution

Q: Pradeep becomes either a Director or a Producer.

Q. A Main Statement is followed by four Statements labelled P, Q, R and S. Choose the ordered pair of the Statements where the first Statement implies the second, and the two Statements are logically consistent with the Main Statement.

Main Statement: Pradeep becomes either a Director or a Producer.

Statement P: Pradeep is a Director

Statement Q: Pradeep is a Producer.

Statement R: Pradeep is not a Director.

Statement S: Pradeep is not a Producer.

Select the correct answer.
a) SP only
b) RQ only
c) Both SP and RQ
d) Neither SP nor RQ
Correct answer: c) Both SP and RQ

Question from UPSC Prelims 2024 CSAT

Explanation : 

Given main statement: Pradeep becomes either a Director or a Producer

Let’s define:
D = Pradeep is a Director
P = Pradeep is a Producer
R = Not Director
S = Not Producer

Analyzing statement pairs:

1. S implies P:
– If S is true (Not Producer)
– From main statement (must be Director or Producer)
– Then D must be true (Director)
This is valid

2. R implies Q:
– If R is true (Not Director)
– From main statement (must be Director or Producer)
– Then P must be true (Producer)
This is valid

Both pairs are logically valid based on the main statement that Pradeep must be either Director or Producer.

Answer: c) Both SP and RQ are valid implications.

Q: Pradeep becomes either a Director or a Producer. Read More »

Q. Age of each of P and Q is less than 100 years but more than 10 years. If you interchange the digits of the age of P, the number represents the age of Q.

Q. Age of each of P and Q is less than 100 years but more than 10 years. If you interchange the digits of the age of P, the number represents the age of Q.

Question: What is the difference of their ages?

Statement-I: The age of P is greater than the age of Q.

Statement-II: The sum of their ages is 11/6 times their difference.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by both the Statements using together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together
Correct answer: a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone

Question from UPSC Prelims 2024 CSAT

Explanation : 

Given:
– P and Q are two-digit ages
– P = 10a + b
– Q = 10b + a where a and b are digits (1-9)

Statement I: P is greater than Q

– This means 10a + b > 10b + a
– Simplifies to a > b
– Multiple values possible
– Not sufficient alone

Statement II: Sum of ages is 11/6 times their difference

– (P + Q) = 11/6 × (P – Q)
– (10a + b) + (10b + a) = 11/6 × [(10a + b) – (10b + a)]
– 11a + 11b = 11/6 × (9a – 9b)
– 66(a + b) = 99(a – b)
– 5b = a

Since a and b must be single digits:
– Only possible solution is a = 5, b = 1
– Therefore P = 51 and Q = 15
Statement II alone is sufficient.

Answer: a) The question can be answered using Statement II alone, but cannot be answered using Statement I alone.

Q. Age of each of P and Q is less than 100 years but more than 10 years. If you interchange the digits of the age of P, the number represents the age of Q. Read More »

Q: What is the time required to download the software? Statement-I: The size of the software is 12 megabytes.

Q: What is the time required to download the software?

Statement-I: The size of the software is 12 megabytes.

Statement-II: The transfer rate is 2.4 kilobytes per second.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together.
Correct answer: c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone

Question from UPSC Prelims 2024 CSAT

Explanation : 

Statement I Alone:

– Knowing only the size (12 MB) isn’t enough to find download time
– Need transfer rate to calculate time

Statement II Alone:

– Knowing only transfer rate (2.4 KB/s) isn’t enough
– Need file size to calculate time

Both Statements Together:
1. Convert 12 megabytes to kilobytes:
12 MB = 12 × 1024 = 12,288 KB

2. Calculate time:
Time = Size ÷ Rate
= 12,288 KB ÷ 2.4 KB/s
= 5,120 seconds
= 1 hour, 25 minutes, 20 seconds

Q: What is the time required to download the software? Statement-I: The size of the software is 12 megabytes. Read More »

Q: What are the values of m and n where m and n are natural numbers?

Q: What are the values of m and n where m and n are natural numbers?

Statement-I: m+n > mn and m > n.

Statement-II: The product of m and n is 24.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together
Correct answer: c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone

Question from UPSC Prelims 2024 CSAT

Explanation : 

Statement I Alone:

1. Rearranging m + n > mn gives (m-1)(n-1) < 1
2. Since m and n are natural numbers, and m > n:
– n must equal 1
– m can be any natural number > 1
This alone doesn’t give unique values.

Statement II Alone:

1. Factors of 24 give these pairs:
(1,24), (2,12), (3,8), (4,6), (6,4), (8,3), (12,2), (24,1)
This alone doesn’t give unique values.

Both Statements Together:
1. From Statement I, n must be 1
2. From Statement II, mn = 24
3. Substituting n = 1:
m × 1 = 24
Therefore m = 24

The unique solution is m = 24 and n = 1.

Answer: c) The question can be answered using both statements together, but cannot be answered using either statement alone.

Q: What are the values of m and n where m and n are natural numbers? Read More »

Statement: India is the world’s largest producer of milk. Conclusion-I: India is the world’s largest exporter of milk.

Statement: India is the world’s largest producer of milk.

Conclusion-I: India is the world’s largest exporter of milk.

Conclusion-II: India does not import milk.

Which one of the following is correct?
a) Only Conclusion-I follows
b) Only Conclusion-II follows
c) Both Conclusion-I and Conclusion-II follow
d) Neither Conclusion-I nor Conclusion-II follows
Correct answer: d) Neither Conclusion-I nor Conclusion-II follows

Question from UPSC Prelims 2024 CSAT

Explanation : 

Conclusion-I: India is the world’s largest exporter of milk.
Analysis: Being largest producer doesn’t mean largest exporter. Production and export are different metrics. India might consume most milk domestically rather than export.

Conclusion-II: India does not import milk.
Analysis: Being largest producer doesn’t mean no imports. A country can both produce and import based on various factors like regional demand and quality requirements.

Answer: d) Neither Conclusion-I nor Conclusion-II follows

Statement: India is the world’s largest producer of milk. Conclusion-I: India is the world’s largest exporter of milk. Read More »

Q. P, Q, R and S appeared in a test. Question: Has P scored more marks than Q?

Q. P, Q, R and S appeared in a test.

Question: Has P scored more marks than Q?
Statement-I: The sum of the marks scored by P and Q is equal to the sum of the marks scored by R and S.

Statement-II: The sum of the marks scored by P and S is more than the sum of the marks scored by Q and R.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together.
Correct answer: d) The Question cannot be answered even by using both the Statements together.

Question from UPSC Prelims 2024 CSAT

Explanation : 

Analyzing Statement I Alone:

P + Q = R + S
This only shows sum of P and Q equals sum of R and S.
Examples:
P = 7, Q = 5, R = 4, S = 8 → P > Q
P = 6, Q = 6, R = 5, S = 7 → P = Q
P = 5, Q = 7, R = 4, S = 8 → P < Q
Statement I alone insufficient.

Analyzing Statement II Alone:

P + S > Q + R
Shows P and S together score more than Q and R.
Examples:
P = 7, S = 5, Q = 5, R = 4 → P > Q
P = 3, S = 6, Q = 4, R = 3 → P < Q
Statement II alone insufficient.

Combining Statements:

From I: P + Q = R + S → P = R + S – Q
From II: P + S > Q + R → S > Q
Substituting: P = R + (S – Q)
Examples:
If R = 35, S = 60, Q = 50 → P = 45 → P < Q
If R = 41, S = 60, Q = 50 → P = 51 → P > Q
Combined statements still insufficient.

Answer: d) The Question cannot be answered even by using both the Statements together.

Q. P, Q, R and S appeared in a test. Question: Has P scored more marks than Q? Read More »

Q. A person buys three articles p, q and r for 50. The price of the article q is 16 which is the least.

Q. A person buys three articles p, q and r for 50. The price of the article q is 16 which is the least.

Question: What is the price of the article p?

Statement-I: The cost of p is not more than that of r.

Statement-II: The cost of r is not more than that of p.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by the Statements using both together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together
Correct answer: c) The Question can be answered by the Statements using both together, but cannot be answered using either Statement alone

Question from UPSC Prelims 2024 CSAT

Explanation : 

Total Cost:
p + q + r = 50
Given q = 16 (the least),
p + r = 34

Statement I: p ≤ r

Possible pairs (p, r):
p = 16, r = 18
p = 17, r = 17
Conclusion: p can be 16 or 17. Statement I alone insufficient.

Statement II: r ≤ p

Possible pairs (p, r):
p = 17, r = 17
p = 18, r = 16
Conclusion: p can be 17 or 18. Statement II alone insufficient.

Using Both Statements Together:
p ≤ r and r ≤ p imply p = r
Thus, p = r = 17
Conclusion: p is uniquely determined as 17 using both statements.

Answer: c) The Question can be answered by the Statements using both together, but cannot be answered using either Statement alone.

Q. A person buys three articles p, q and r for 50. The price of the article q is 16 which is the least. Read More »

Question: Is (x + y) an integer? Statement-I: (2x+y) is an integer. Statement-II: (x+2y) is an integer.

Q: Is (x + y) an integer?

Statement-I: (2x+y) is an integer.

Statement-II: (x+2y) is an integer.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone
b) The Question can be answered by using either Statement alone
c) The Question can be answered by using both Statements together, but cannot be answered using either Statement alone
d) The Question cannot be answered even by using both the Statements together.
Correct answer: d) The Question cannot be answered even by using both the Statements together.

Question from UPSC Prelims 2024 CSAT

Explanation : 

Objective: Determine if (x + y) is an integer.

Analysis:

1. Solving the System:
Let 2x + y = A (where A is an integer).
Let x + 2y = B (where B is an integer).

Multiply equation (1) by 2:
4x + 2y = 2A

Subtract equation (2):
3x = 2A – B
x = (2A – B)/3

Substitute x back:
y = A – 2x = A – 2(2A – B)/3 = (-A + 2B)/3

Therefore:
x + y = (2A – B)/3 + (-A + 2B)/3 = (A + B)/3

For (x + y) to be integer, A + B must be divisible by 3.

2. Evaluating Statements:
Using Statement I Alone: Knowing 2x + y is integer (A) doesn’t guarantee x + y is integer.

Using Statement II Alone: Knowing x + 2y is integer (B) doesn’t guarantee x + y is integer.

Using Both Statements Together: Even with both A and B known, x + y = (A + B)/3 is not guaranteed to be integer unless A + B is divisible by 3, which isn’t assured.

Conclusion:
Even with both statements, there’s insufficient information to determine whether (x + y) is an integer.

Answer: The Question cannot be answered even by using both the Statements together.

Question: Is (x + y) an integer? Statement-I: (2x+y) is an integer. Statement-II: (x+2y) is an integer. Read More »

Q. There are three distinct prime numbers whose sum is a prime number.

Q. A Question is given followed by two Statements I and II. Consider the Question and the Statements.

There are three distinct prime numbers whose sum is a prime number.

Question: What are those three numbers?
Statement-1: Their sum is less than 23.

Statement-II: One of the numbers is 5.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.
b) The Question can be answered by using either Statement alone.
c) The Question can be answered by using both the Statements together, but cannot be answered using either Statement alone.
d) The Question cannot be answered even by using both the Statements together.
Correct answer: a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.

Question from UPSC Prelims 2024 CSAT

Explanation : 

Using Statement I Alone:

Primes less than 23: 2, 3, 5, 7, 11, 13, 17, 19.
Possible Combinations:
(2, 3, 5) -> Sum = 10 (Not prime)
(2, 3, 7) -> Sum = 12 (Not prime)
(3, 5, 11) -> Sum = 19 (Prime)
… (Other combinations either do not sum to a prime or exceed the sum limit)

Conclusion: The only valid combination under this statement is (3, 5, 11).

Using Statement II Alone:

Given: One of the numbers is 5.
Possible Combinations (without sum constraint):
(3, 5, 11) -> Sum = 19 (Prime)
(5, 7, 11) -> Sum = 23 (Prime)
(5, 7, 17) -> Sum = 29 (Prime)
(5, 13, 17) -> Sum = 35 (Not prime)
…and several others.

Conclusion: There are multiple valid combinations, such as (3, 5, 11), (5, 7, 11), (5, 7, 17), etc. Therefore, Statement II alone does not uniquely determine the answer.

Final Conclusion:
Statement I alone is sufficient to uniquely identify the three primes as (3, 5, 11).
Statement II alone is not sufficient as it allows for multiple valid combinations.

Answer: The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.

Q. There are three distinct prime numbers whose sum is a prime number. Read More »

Q. If the average marks in a class are 60, then what is the number of students in the class?

Q. A Question is given followed by two Statements I and II. Consider the Question and the Statements.

Q. If the average marks in a class are 60, then what is the number of students in the class?

Statement-I: The highest marks in the class are 70 and the lowest marks are 50.

Statement-II: Exclusion of highest and lowest marks from the class does not change the average.

Which one of the following is correct in respect of the above Question and the Statements?
a) The Question can be answered by using one of the Statements alone, but cannot be answered using the other Statement alone.
b) The Question can be answered by using either Statement alone.
c) The Question can be answered by both the Statements together, but cannot be answered using either Statement alone.
d) The Question cannot be answered even by using both the Statements together
Correct answer: d) The Question cannot be answered even by using both the Statements together

Question from UPSC Prelims 2024 CSAT

Explanation : 

To determine the number of students in the class based on the given information, let’s analyze both statements individually and then consider them together.

Given:- Average marks = 60

Question:- What is the number of students in the class?

Analysis:

Statement I:
– Information Provided:
– Highest marks = 70
– Lowest marks = 50
– Implications:
– Without additional information about the distribution of marks or the total sum of marks, knowing just the highest and lowest marks doesn’t help in determining the number of students.
– Conclusion: Statement I alone is insufficient to determine the number of students.

Statement II:
– Information Provided:
– Removing the highest and lowest marks doesn’t change the average.
– Mathematical Implication:
– Let the number of students be n.
– Total sum of marks = Average × Number of students = 60n
– After removing highest and lowest marks:
– New sum = 60n – 70 – 50 = 60n – 120
– New number of students = n – 2
– New average = 60
– Setting up the equation:
60n – 120/n – 2 = 60
60n – 120 = 60(n – 2)
60n – 120 = 60n – 120
– The equation simplifies to 0 = 0, which is always true regardless of the value of n.
– Conclusion: Statement II alone is insufficient to determine the number of students.

Combining Statements I and II:

– Even when combining both statements:
– Highest Marks: 70
– Lowest Marks: 50
– Average remains 60 after exclusion.
– Attempts to solve for n with combined information still do not yield a unique solution for the number of students.
– Conclusion: Even together, the statements are insufficient to determine the exact number of students.

Final Answer: d) The Question cannot be answered even by using both the Statements together

Q. If the average marks in a class are 60, then what is the number of students in the class? Read More »