gmattesttaker2 wrote:
Each of the following numbers has two digits x'ed out. Which of the numbers could be the number of hours in n days, where n is an integer?
(A) 25x,x06
(B) 50x,x26
(c) 56x,x02
(D) 62x,x50
(E) 65x,x20
OA: E
This is a divisibility question in disguise.
There are 24 hours in 1 day.
Since 24 is divisible by 4, the number of hours in n days must be divisible by 4.
For example, there are
48 hours in 2 days,
72 hours in 3 days,
96 hours in 4 days,
120 hours in 5 days,
144 hours in 6 days,
168 hours in 7 days, etc.
Notice that
48,
72,
96,
120,
144, and
168 are all divisible by 4.
IMPORTANT: To determine whether an integer is divisible by 4, we need only check the number formed by the
last 2 digits. If that 2-digit number is divisible by 4, the entire integer is divisible by 4.
For example, we know that 125431
28 is divisible by 4 because
28 is divisible by 4.
Likewise, we know that 328731
17 is NOT divisible by 4 because
17 is NOT divisible by 4.
When we check the last 2 digits of the answer choices, we see that only
E is such that the number created by the last 2 digits (
20) is divisible by 4. So,
E is the only value that could be divisible by 4.
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
