Question

Alia is 9 years older than her twin brothers. If they are x years old, find the mean age of the three children in simplest terms.

Answer 1

The twin brothers are each x years old.

So, their ages are: x, x

Alia is 9 years older than her twin brothers,

So, her age is x + 9

Thus, the three children’s ages are:

x, x, x + 9

Sum of ages = x + x + (x + 9) = 3x + 9

Number of children = 3

Mean = `"Sum of ages"/"Number of children"`

 = `(3x + 9)/3`

= x + 3

∴ The mean age of the three children = x + 3