Question

in a class the ratio of girls to boys is 4:7 if the class contains 28 boys how many girls are there??

Answer 1

if ratio of girls is 4 x and boys 7 x and 7x =28 then x=28/7= 4 .
4x = 4×4=16
no. of girls in class is 16

Answer 2

let the number of girls =y
number of boys =28
Ratio of girls to boys=4:7
so, 4:7=y:28
product of means = product of extremes
=> 4 x 28=7 x y
=>112=7y
=>y =122/7
=>y =16
therefore number of girls in a class =16

Hope it helps :)