Question 1143742
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Given that there are 4/5 as many girls as boys, you can treat the "4/5" as a ratio -- girls:boys = 4:5.  So use the general procedure for setting up a problem involving ratios:<br>
let 4x = # of girls
let 5x = # of boys<br>
Then<br>
{{{4x+5x = 9x = 27}}}
{{{x = 3}}}<br>
The number of boys is 5x = 5(3) = 15.