A half of what John's age was 4 years ago is equal to one third of what it will be in 5 years' time. How old is John now? Explain your workings

Answer 1

Let John's present age be x
Four years ago John was x-4
Half of John's age 4 years ago = (x-4)/2

John's age in 5 years from now = x+5
a third of his age 5 from now = (x+5)/3

(x-4)/2 = (x+5)/3
cross-multiply
3x - 12 = 2x + 10
x = 22

So John is now 22 years old

check:
4 years ago he would have been 18
5 years from now he will be 27
is half of 18 equal to a third of 27 ? YES