Quantitative Comparisions

[patrakakali79]

The ratio of the no. of boys to the no. of girls in the class was 4 to 3.After 2 new boys and 3 new girls joined the class,the ratio became 6 to 5.

Column A Column B
Original no. of boys in the class 18

Source : Kaplan GRE Math

[tommywallach]

Hey Patra,

I'm always happy to answer question, but it's typically better if you give some amount of description of where you got caught up on the question, as opposed to just how to do it top to bottom. That way I can respond to your exact issue, instead of simply providing a solution.

In this example, we can think of the original number of boys and girls like this:

Boys: 4x
Girls: 3x

(Where x is the "multiplier," a concept we often use in ratio questions).

Now we can respond to the change:

New Boys: 4x + 2
New Girls: 3x + 3

Finally, we write our final equation:

(4x + 2)/(3x + 3) = 6/5

Cross-multiply and solve:

20x + 10 = 18x + 18
2x = 8
x = 4

This is our multiplier. Original boys was 4x, so 4 * 4 = 16.

The answer is (B).

[patrakakali79]

Hi Tommy,
Thanks for the explanation.Next time I'll surely provide some description of where i got stumped in a question.

[tommywallach]

Thanks Patra(k)!

-t