Updates
UPSC Prelims 2024CSATLogical ReasoningData Sufficiency - Number Properties

Q68. A Question if given followed by two Statements I and
II. Consider the Question and the Statements. Question : 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 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

Detailed Solution

✓ Correct Answer: Option D

We need to determine if (x+y) is an integer. **Statement I: (2x+y) is an integer.** - Let x = 0.5, y = 1. Then 2x+y = 2(0.5)+1 = 1+1 = 2 (integer). But x+y = 0.5+1 = 1.5 (not an integer).

- Let x = 1, y = 1. Then 2x+y = 2(1)+1 = 3 (integer). And x+y = 1+1 = 2 (integer). Since (x+y) can be an integer or not, Statement I alone is insufficient. **Statement II: (x+2y) is an integer.** - Let x = 1, y = 0.5.

Then x+2y = 1+2(0.5) = 1+1 = 2 (integer). But x+y = 1+0.5 = 1.5 (not an integer). - Let x = 1, y = 1. Then x+2y = 1+2(1) = 3 (integer). And x+y = 1+1 = 2 (integer). Since (x+y) can be an integer or not, Statement II alone is insufficient.

**Combining Statement I and Statement II:** We have: (2x+y) = K (an integer) and (x+2y) = M (an integer). Adding these two equations: (2x+y) + (x+2y) = K + M 3x + 3y = K + M 3(x+y) = K + M.

Since K and M are integers, K+M is also an integer. So, 3(x+y) is an integer. However, if 3(x+y) is an integer, (x+y) itself is not necessarily an integer. For example, if x=1/3 and y=1/3: - 2x+y = 2/3 + 1/3 = 1 (integer).

- x+2y = 1/3 + 2/3 = 1 (integer). - But x+y = 1/3 + 1/3 = 2/3 (not an integer). Therefore, even with both statements combined, we cannot definitively say if (x+y) is an integer.

This question tests data sufficiency and properties of integers and rational numbers.

Ace UPSC with AI-powered Practice

LearnPro's test series adapts to your weak topics and shows real analytics.

Explore Courses →

Our Courses

72+ Batches

Our Courses
Contact Us