Theory question 102
Linear and Simultaneous EquationsSonny is twice as old as Wale. Four years ago, he was four times as old as Wale. When will the sum of their ages be 66?
Show the model answer
Model answer
Let Wale be y, Sonny 2y. Four years ago: 2y − 4 = 4(y − 4), so 2y = 12 and y = 6. Sonny is 12.
In n years: (12 + n) + (6 + n) = 66, so 2n = 48 and n = 24.
The sum of their ages will be 66 in 24 years' time.
Explanation
Both ages increase by n, so the sum increases by 2n.