Hello everyone,

I am trying to solve a problem that i came across in my GRE booklet, it seems that the answer i came up with is different from the booklet...

A mixture of 12 oz of vinegar and oil is 40% vinegar, where all of the measurements are by weight. How many ounces of oil must be added to the mixture yto produce a new mixture that is only 25% vinegar?I conceptualised the problem as such: If the 12 oz vinegar/ oil mixture is 40% vinegar, then it is 60% oil. The mixture therefore has 4.8 oz vinegar and 7.2 oz oil. I therefore want to increase the oil content by 15%, thereby decreasing the vinegar content by the same margin.

so i calculated as follows:

7.2 x 1.15 = 8.28.

8.28 - 7.2 = 1.08

I therefore concluded that 1.08 oz oil have to be added to make a mixture that is only 25% vinegar.

However the answer given in the booklet is 7.2 oz. Can anyone explain where I went wrong?

Thanks