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

1/2
1/3
1/4
1/5
1/6

We can plug in the answers, which represent the fraction saved each month.

Answer choice C: 1/4
Let the monthly pay = 4.
Amount saved each month = (1/4)4 = 1, so the amount not saved each month = 3.
Amount saved over the whole year = 12*1 = 12.
(Total saved)/(monthly not saved) = 12/3 = 4.
Since it is required that (total saved)/(monthly not saved) = 3, too high a fraction is being saved.
Eliminate A, B and C.

Answer choice D: 1/5
Let the monthly pay = 5.
Amount saved each month = (1/5)5 = 1, so the amount not saved each month = 4.
Amount saved over the whole year = 12*1 = 12.
(Total saved)/(monthly not saved) = 12/4 = 3.
Success!

The correct answer is D.