SOLUTION: 3/5 of the pupils in a class are girls. There are 12 boys in the class. How many girls are in the class?

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Question 826063: 3/5 of the pupils in a class are girls. There are 12 boys in the class. How many girls are in the class?
Found 2 solutions by josgarithmetic, stanbon:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
b boys
g girls
c class size


b%2Bg=c; b=12. %283%2F5%29c=g. 12%2Bg=c.
The last two equations are our system to solve.

SYSTEM:
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%283%2F5%29c=g
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g%2B12=c
-----------------

%283%2F5%29c=g
%283%2F5%29%28g%2B12%29=g
3%28g%2B12%29=5g
3g%2B36=5g
36=2g
highlight%28g=18%29
'
c=g%2B12
c=18%2B12
highlight%28c=30%29

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
3/5 of the pupils in a class are girls. There are 12 boys in the class. How many girls are in the class?
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Let # in the class be "x";
(2/5)x = 12
x = (5/2)12
x = 30
======
# of girls = (3/5)30 = 18
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Cheers,
Stan h.
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