Bunuel
What is the remainder when integer n is divided by two?
(1) When n is divided by 5, the remainder is even.
(2) When n is divided by 7, the remainder is even.
Solution: Pre-analysis: We are asked for the remainder when n is divided by 2
We know when any integer n is divided by 2, the remainder can be 0 (when n is even) or 1 (when n is odd)
Therefore,
the question is technically asking us if integer n is even or oddStatement 1: When n is divided by 5, the remainder is even
According to this statement, \(n\) can be \(5k, 5k+2, 5k+4, 5k+6\) and so on
The value of n thus can be both even or odd based on the value of \(k\)
Thus, statement 1 alone is not sufficient and we can eliminate options A and D
Statement 2: When n is divided by 7, the remainder is even
Similar to statement 1, the value of \(n\) can be \(7p, 7p+2, 7p+4, 7p+6\) and so on
The value of n thus can be both even or odd based on the value of \(p\)
Thus, statement 2 alone is also not sufficient and we can eliminate option B
Combining: Let's take 2 cases:
\(n = 35\) (odd) and when n=35 is divided by 5 and 7, the remainder is even i.e., 0
\(n = 70\) (even and when n=35 is divided by 5 and 7, the remainder is even i.e., 0
Thus,
even after combining, it is not possible to know if n is even or odd Hence the right answer is
Option E