PREP数学 求教

cappuccino202

如图，没思路啊。。。第一次做PREP，数学才49，打击。。。

sdcar2010

category              manager    director
number                     x               y
average salary          m              d
subtotal salary        m*x           d*y

average salary for the whole group = (m*x + d*y) /(m+d)

We need to find the value of y/(x+y)

1) m+5k = (m*x + d*y) /(x+y)
2) d - 15k = (m*x + d*y) /(x+y)

Apparently if combining 1) and 2), we have m = (d - 20k)

So (d-20k) + 5k = [(d-20k)*x + d*y]/(x+y)
d - 15k = d -(20k)*x/(x+y)
15/20 = x/(x+y)
y/(x+y) = 1/4

CCCCCCCCcc

runningcandy

ls同学的方法亮了 受教~~

sdcar2010

LZ can search for weighter average and GMAT to find general methods to tackle this type of questions in the future.

cappuccino202

嗯嗯，谢谢2L 3L，就是觉得用普通的方法很花时间啊~~~