Problem Solving

The ratio of the number of boys to the number of girls in a certain school club is 3 : 4. If there are 5 more girls than boys in the club, how many girls are in the club?
A. 7
B. 8
C. 12
D. 15
E. 20

Could someone give me an easy explanation to this?

Let x be the number of boys and y be the number of girls in a club.
AS per the first sentence in the problem, the ratio of boys to girls=3:4
=> x:y=3:4
=>x/y=3/4...................(1)
Now as per the second sentence there are 5 more girls than boys in the club.
Therefore y-x=5
=> y=x+5..........................(2)
Putting the value of y as per equation 2 in the ratio equation (1) we get,
x/(x+5)=3/4
Therefore x=15
Hence number of girls in the club y=x+5=20
Ans E

thanks GMAT WAR

angxif -----

I just wanted to show another method of solving.

Lets take a table format,

Boys Girls T(total)

Ratios 3 4 7

Constant x x x

Values 3x 4x 7x

Now, the given condition is 5 girls more than Boys. We can write this as,
Girls = Boys + 5
Substitute values from the above table,
4x = 3x + 5
then, x = 5

Question asked for no.of girls in the club, then 4x = 4*5=20.

HTH, GOOD LUCK,

Thanks,
Rajesh,
Loves GMAT....!!!!