Problem Solving

Bob's take-home pay last year was the same each month, and he saved the same fraction of his take-home pay each month. The total amount of money that he had saved at the end of the year was 3 times the amount of that portion of his monthly take-home pay that he did not save. If all the money he saved last year was from his take-home pay, what fraction of his take-home pay did he save each money

A) 1/2
B) 1/3
C) 1/4
D) 1/5
E) 1/6

In this problem we cannot assign numbers.
So let us represent each statement with a equation.

Each month the employee saved "s" dollars and did not save "ns" dollars.
The total earnings for each month is "s" +"ns"

So at the end of the year he would have saved 12 s which is equal to 3 ns (given).

So the equation is

12 s = 3 ns
==> ns = 4s there fore his monthly saving is 5 s ( 4s +s money he did not save + money saved).

Therefore the proportion s/5s = 1/5

Option D