The ratio of girls to boys is 2:3 and there are 20 people in the class, how many are girls and boys?

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Answer 1 · 2015-06-02T18:06:58

Lets name #b# the number of boys and #g# the number of girls
#b+g=20#
#g/b=2/3# so #g=(2b)/3# ( we multiply by #b# on each side )

We can thus replace g in the equation :

#b+(2b)/3=20#

We want to put on the same denominator :

#(3b)/3+(2b)/3=20#

#(5b)/3=20#

#5b=60# ( we multiply by #3# on each side )
#b= 12# ( we divide by #5# on each side )

We can thus now find #g# :

#b+g=20#
#12+g=20#
#g=20-12# ( we substract #12# on each side )
#g=8#

There are thus #12# boys and #8# girls in the class