Posted by **jane** on Saturday, December 1, 2012 at 10:52pm.

The ratio of the number of girls to the number of boys in a stamp club was 3 : 2 last year. When 15 boys joined the club this year, the ratio became 2 : 3. Find the total number of children in the club this year.

- math -
**Reiny**, Saturday, December 1, 2012 at 11:52pm
let the number of girls be 3x and the number of boys 2x

(notice 3x : 2x = 3 : 2 )

after the addition of boys

number of girls = 3x

number of boys = 2x + 15

3x : 2x+15 = 2:3

3x/(2x+15) = 2/3

9x = 4x + 30

5x = 30

x = 6

current number of girls = 18

current number of boys = 27

so number of children in the club now

= 3x + 2x+15 = 5x + 15

= 5(6) + 15 = 45

check:

original: girls = 18, boys = 12, notice ratio is 18:12 = 3:2

after: girls = 18 , boys = 27 , notice 18:27 = 2:3

and 18+27 = 45

all is well.

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