If 'n' is any odd number greater than 1, then
n(n² − 1)
- is divisible by 15 always
- is divisible by 24 always
- is divisible by 48 always
- is divisible by 96 always
- is divisible by 100 always
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Answer: B official key
Approach: n(n² − 1) = (n − 1)·n·(n + 1) is a product of three consecutive integers.
Solution:
n(n² − 1) = (n − 1)·n·(n + 1).
Any three consecutive integers contain a multiple of 3 → divisible by 3.
n is odd, so (n − 1) and (n + 1) are consecutive even numbers; one of them is a multiple of 4 → product of the two is divisible by 2 × 4 = 8.
So the expression is divisible by 3 × 8 = 24 for every odd n > 1.
Check n = 3: 3 × 8 = 24 (divisible by 24, not by 48/96/100/15).
Why the other options are wrong:
- A (15): n = 3 gives 24, not divisible by 5.
- C (48), D (96): n = 3 gives 24 — fails.
- E (100): n = 3 gives 24 — fails.
Cetking shortcut: Plug the smallest allowed value n = 3 → 24. Every 'always' option larger than 24 or not dividing 24 is out instantly.
Answer: B



















































