Hi april24,
This DS question is perfect for TESTing values:
We're asked for the remainder when (n-1)(n+1) is divided by 24.
Fact 1: n is NOT divisible by 2.
This means that n must be ODD, so we have to restrict our TESTS to odd numbers
If n = 1, then (0)(1) = 0; 0/24 = 0 r 0
If n = 3, then (2)(4) = 8; 8/24 = 0 r 8
Different answers means Fact 1 is INSUFFICIENT
Fact 2: n is NOT divisible by 3
This means that n is NOT a multiple of 3.
If n = 1, then (0)(1) = 0; 0/24 = 0 r 0
If n = 2, then (2)(3) = 6; 6/24 = 0 r 6
Different answers means Fact 2 is INSUFFICIENT
Together, n is NOT divisibly by 2 nor 3, which severely restricts the possibilities:
If n = 1, then (0)(1) = 0; 0/24 = 0 r 0
If n = 5, then (4)(6) = 24; 24/24 = 1 r 0
If n = 7, then (6)(8) = 48; 48/24 = 2 r 0
Answers are consistent, so combined it's SUFFICIENT
Final Answer: C
GMAT assassins aren't born, they're made,
Rich
remainder DS question
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