CSAT 2024

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 »

Q. A certain amount was distributed among X, Y and Z.

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

A certain amount was distributed among X, Y and Z.

Question: Who received the least amount?

Statement-1: X received 4/5 of what Y and Z together received.

Statement-II: Y received 2/7 of what X and Z together received.

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 : 

To determine who received the least amount among X, Y, and Z, let’s analyze the given statements:

Statement I: Given: X = 4/5(Y + Z)

Implication: The total amount distributed, T = X + Y + Z. Substituting from the statement:
T = 4/5(Y + Z) + Y + Z = 9/5(Y + Z)
Y + Z = 5/9T
X = 4/9T
Analysis: While we know X = 4/9T and Y + Z = 5/9T, we cannot determine the individual values of Y and Z. Without knowing how Y and Z are divided, we cannot conclusively identify who received the least.

Statement II: Given: Y = 2/7(X + Z)

Implication:
Let X + Z = a. Then, Y = 2/7a and T = a + 2/7a = 9/7a
Y = 2/9T
X + Z = 7/9T
Analysis: Even though we know Y = 2/9T, without the individual values of X and Z, it’s unclear whether Y is the least or if X or Z could be lesser based on their distribution.

Using Both Statements Together:

From Statement I: X = 4/9T
From Statement II: Y = 2/9T and X + Z = 7/9T
Substituting:
Y = 2/7(X + Z) = 2/7 × 7/9T = 2/9T
X = 4/9T
Z = 3/9T
Conclusion: The distribution ratios are X:Y:Z = 4:2:3. Clearly, Y receives the least amount.

Q. A certain amount was distributed among X, Y and Z. Read More »

Question: What are the unique values of x and y, where x, y are distinct natural numbers? Statement-I: x / y is odd. Statement-II: xy = 12

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

Question: What are the unique values of x and y, where x, y are distinct natural numbers?

Statement-I: x / y is odd.

Statement-II: xy = 12

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 : 

To determine the unique values of x and y (distinct natural numbers) that satisfy the given conditions, let’s analyze each statement individually and then consider them together.

Statement I: x/y is odd.

Interpretation: For x/y to be an odd integer, x must be an odd multiple of y. This implies that y must be a divisor of x, and the quotient x/y must be an odd number.

Limitations: Without additional information, there are multiple pairs (x, y) that can satisfy this condition. For example:
– x = 3, y = 1 (since 3/1 = 3 is odd)
– x = 9, y = 3 (since 9/3 = 3 is odd)

Conclusion: Statement I alone is insufficient to determine unique values of x and y.

Statement II: xy = 12.

Interpretation: The product of x and y is 12. Considering that x and y are distinct natural numbers, the possible pairs are:
– (1, 12)
– (2, 6)
– (3, 4)

Limitations: Multiple valid pairs satisfy this condition.

Conclusion: Statement II alone is insufficient to determine unique values of x and y.

Combining Statements I and II:

Now, let’s use both statements together.

1. From Statement II, the possible pairs are (1, 12), (2, 6), and (3, 4).

2. Applying Statement I (x/y is odd) to each pair:
– (1, 12): 1/12 is not an integer, so this pair is invalid.
– (2, 6): 2/6 = 1/3 is not an integer, so this pair is invalid.
– (3, 4): 3/4 is not an integer, so this pair appears invalid at first glance.

However, there’s a misunderstanding here. For x/y to be an odd integer, x must be a multiple of y, and the quotient must itself be odd.

Re-examining the possible pairs:
– (12, 1): 12/1 = 12 (Even)
– (6, 2): 6/2 = 3 (Odd)
– (4, 3): 4/3 is not an integer.

Valid Pair: (6, 2) since 6/2 = 3 is an odd integer.

Conclusion: Using both statements together, the unique values are x = 6 and y = 2.

Therefore, option c is the correct choice.

Question: What are the unique values of x and y, where x, y are distinct natural numbers? Statement-I: x / y is odd. Statement-II: xy = 12 Read More »

Q. A person walks 100 m Westward, then turns left and walks 100 m. He then takes a 225° turn clockwise. In which direction is he walking now?

Q. A person walks 100 m Westward, then turns left and walks 100 m. He then takes a 225° turn clockwise. In which direction is he walking now?

a) South-West
b) South-East
c) North-West
d) North-East
Correct answer: d) North-East

Question from UPSC Prelims 2024 CSAT

Explanation : 

Initial Movement:
Direction: West
Action: Walks 100 meters West.

First Turn:
Turn: Left
From West, turning left means facing South.
Action: Walks 100 meters South.

Second Turn:
Turn: 225° clockwise from South
Understanding the Turn:
– Starting Direction: South (which is 180° on a compass)
– Clockwise Turn: Adding 225° to the current direction.
– Calculation: 180° (South) + 225° = 405°
– Since 405° is equivalent to 45° (405° – 360°), the final direction is 45°, which corresponds to North-East on a compass.

Final Direction: North-East, Answer: d) North-East

A person walks 100 m Westward

Q. A person walks 100 m Westward, then turns left and walks 100 m. He then takes a 225° turn clockwise. In which direction is he walking now? Read More »

Q. A person walks 100 m straight from his house, turns left and walks 100 m

Q. A person walks 100 m straight from his house, turns left and walks 100 m,

again turns left and walks 300 m, then turns right and walks 100 m to reach his office. In which direction does he walk initially from his house if his office is exactly in the North-East direction?
a) North-West
b) West
c) South
d) South-West
Correct answer: c) South

Question from UPSC Prelims 2024 CSAT

Explanation : 

Let’s analyze the person’s movements step by step to determine the initial direction:

1. Initial Direction: Suppose the person starts by walking South.

2. First Movement:
– Walks 100 m South.
– Position: (0, -100).

3. First Turn (Left):
– From South, turning left means facing East.
– Walks 100 m East.
– Position: (100, -100).

4. Second Turn (Left):
– From East, turning left means facing North.
– Walks 300 m North.
– Position: (100, 200).

5. Third Turn (Right):
– From North, turning right means facing East again.
– Walks 100 m East.
– Final Position: (200, 200).

The final position (200, 200) places the office North-East of the house, which matches the given condition.

Answer: c) South

A person walks 100 m

Q. A person walks 100 m straight from his house, turns left and walks 100 m Read More »

Q. Let p and q be positive integers satisfying p

Q. Let p and q be positive integers satisfying p<q and p+q=k.

What is the smallest value of k that does not determine p and q uniquely?
a) 3
b) 4
c) 5
d) 6
Correct answer: c) 5

Question from UPSC Prelims 2024 CSAT

Explanation : 

Let p and q be positive integers

To determine the smallest value of k that does not uniquely determine the positive integers p and q (with p < q and p + q = k), let’s evaluate each option:

1. k = 3
– Possible pairs: (1, 2)
– Unique pair: Yes.

2. k = 4
– Possible pairs: (1, 3)
– Unique pair: Yes. (Note: (2, 2) is invalid since p < q.)

3. k = 5
– Possible pairs: (1, 4) and (2, 3)
– Unique pair: No. There are two distinct pairs.

4. k = 6
– Possible pairs: (1, 5) and (2, 4)
– Unique pair: No. There are two distinct pairs.

The smallest k where multiple pairs (p, q) satisfy the conditions is k = 5.

Q. Let p and q be positive integers satisfying p<q and p+q=k. Read More »

Q. 32^5 + 2^27 is divisible by a) 3 b) 7 c) 10 d) 11

Q. 32^5 + 2^27 is divisible by

a) 3
b) 7
c) 10
d) 11

Correct answer: c) 10

Question from UPSC Prelims 2024 CSAT

Explanation : 

32^5 + 2^27

To determine which of the given options divides 32^5 + 2^27, let’s simplify and analyze the expression step-by-step.

Simplify the Expression First, express everything in terms of powers of 2: 32 = 2^5 implies 32^5 = (2^5)^5 = 2^25

2^27 remains as is.

So, the expression becomes: 32^5 + 2^27 = 2^25 + 2^27 = 2^25(1 + 2^2) = 2^25 × 5

This shows that the expression is divisible by 2^25 and 5, and consequently by 2 × 5 = 10.

Q. 32^5 + 2^27 is divisible by a) 3 b) 7 c) 10 d) 11 Read More »