Question

There are 1800 gym members in total, 3/4 are aged 25-59, 1/5 are over 60 and the remainder are under 25, how many members are under 25years

Answer 1

If
`x` is the number of members under 25, then we have


`1800=\frac34\cdot1800+\frac15\cdot1800+x\implies x=90`