Question

The ratio of the numbers of boys and girls in a class is 5 : 6. If the number of boys in the class is 30, find the number of girls.

Answer 1

Ratio of the number of boys to the number of girls in the class = 5:6$=\frac{5}{6}$
Number of boys in the class = 30
Let the number of girls in the class be x.
∴ Ratio of the number of boys to the number of girls = 30:x$=\frac{30}{x}$

Because the two ratios are the same, $\frac{5}{6}=\frac{30}{x}$.
Also, because the numerator of the second ratio is six times the numerator of the first ratio, x = 6 × 6 = 36.
Thus, the number of girls in the class is 36.