Question

A grade has 81 girls and 72 boys. The grade is split into groups that have the same ratio of girls to boys as the whole grade. How many girls are in a group that has 16 boys?

Answer 1

$\bf \cfrac{girls}{boys}\quad girls:boys\qquad \cfrac{81}{72}\implies \cfrac{9}{8}\qquad \qquad \cfrac{9}{8}=\cfrac{\stackrel{girls}{g}}{\stackrel{boys}{16}}\implies \cfrac{9\cdot 16}{8}=g$