arkle wrote:

If two typists can type two pages in two minutes, how many typists will it take to type 18 pages in six minutes?

A. 3

B. 4

C. 6

D. 12

E. 36

Could anyone plz explain a robust approach to solve above mentioned problem.I mostly get confused in RT=W probs.Thanks!

2 typists 2 pages 2 minutes

2 typists 2*9=18 pages 2*9=18 minutes (9 times more pages, 9 times more time)

2*3=

6 typists 18 pages 18/3=6 minutes (need 3 times faster, should increase number of typists by the same factor 3)

Answer C

This question is about direct and inverse proportionality.

RxT=W (rate x time = work)

If work is constant, then R and T are inversely proportional, meaning if R increases, T decreases and vice-versa.

If R is constant, then T and W are directly proportional, meaning if T increase, W increases (more time, more job done).

If T is constant, then R and W are again directly proportional, meaning if R increases, W increases (faster rate, more job done).

In the above approach, first if we increase the number of pages (more work must be done), but we stay with the same number of typists, we need proportionally more time. Here, time and work are directly proportional.

Then, for the same number of pages (same work), if we want the job done faster, we need more typists. Now, number of typists and time are inversely proportional.

This type of question reminds me of a home-work that would upset many parents (lamenting that this is insane

):

If one and a half chicken lay in a day and half one egg and a half, how many eggs will lay three chicken in three days?

Who heard of half chickens laying half eggs...those math teachers gone mad!!!

_________________

PhD in Applied Mathematics

Love GMAT Quant questions and running.