Question 1108447
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You can solve this using a proportion.<br>
The boys are 45%, so the girls are 55%.  Since the number of girls is 77, if x is the number of boys then
{{{45:55 = x:77}}}
{{{9:11 = x:77}}}
{{{x = 63}}}<br>
So there are 63 boys; then the total number of students is 77+63 = 140.<br>
Alternatively, you could just say since 55% of the total number of students (the girls) is 77, if x is the total number of students then
{{{0.55x = 77}}}
{{{x = 77/0.55 = 140}}}