the ratio of the number of boys to the number of girls in a class is 5:4. if there are 15 boys, how many girls are there

2 answers

b = number of boys

g = number of girls

The ratio of the number of boys to the number of girls in a class is 5:4 means:

b / g = 5 / 4

Cross multiply

4 b = 5 g

Divide both sides by 5

4 / 5 b = g

g = 4 / 5 b = 0.8 b = 0.8 ∙ 15 = 12

Check results:

b / g = 15 / 12 = 3 ∙ 5 / 3 ∙ 4 = 5 / 4
Answer is 12