Bunuel
If \(P = k^3 - k^2\), where k and P are positive integers, is P divisible by 4?
(1) \(k = (10x)n + 5^4\) where x and n are positive integers and n > 1.
(2) \((2n + 1)k\) leaves a remainder when divided by 2; n is a positive integer
\(P = k^2(k-1)\)
Inference : For P to be divisible by 4
- If k = even, k^2 will be divisible by 4. Hence P is divisible by 4.
- If k = odd, (k-1) should be divisible by 4.
Statement 1\(k = (10x)n + 5^4\) where x and n are positive integers and n > 1.
k = even + odd = odd
We have established that k is odd, now we need to find if k - 1 is divisible by 4.
It's given that x & n > 1, so k-1 will always be an even integer which is divisible by 4.
Statement 1 is sufficient and we can eliminate B, C and E.
Statement 2 \((2n + 1)k\) leaves a remainder when divided by 2; n is a positive integer
If a number leaves a remainder when divided by 2, then the number is an odd.
Therefore, (2n+1)k is odd. (2n+1) is odd, therefore we can conclude that k is odd.
Now we need to determine if k-1 is divisible by 4.
Say k = 3; k - 1 = 2. k-1 is not divisible by 4.
k = 5; k - 1 = 4. k-1 is divisible by 4.
As we are getting two different answers, we can eliminate B.
Option A