romitvsingh wrote:If 18 is 15 percent of 30 percent of a certain number, what is the number?
A) 9
B) 36
C) 40
D) 81
E) 400
A quick approach here is to plug in numbers, beginning with C.
C. Is it true that 18 is 15 percent of 30 percent
40?
Well, 30% of 40 is 12, and 15% of 12 is definitely not 18
So, the answer is not C (40). In fact, we need a starting number that is greater than 40.
D. Is it true that 18 is 15 percent of 30 percent
81?
Well, 30% of 81 is less than 30, and 15% of 30 is definitely not 18
So, the answer is not D (81). In fact, we need a starting number that is greater than 81.
From here, we can select E, without even checking it.
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
