Matching a formula to a given context

Question 2

In 3 year's time Michael will be twice as old as Alison. Which one of the following rules represents Michael's age now in terms of Alison's age now?

a Michael's age now = 2(Alison's age now + 3).

b Michael's age now = (Alison's age now + 3) ÷ 2.

c Michael's age now = 2 Alison's age now − 3.

d Michael's age now = 2 Alison's age now + 3.

Solution

In 3 years' time both Michael and Alison will be 3 years older!

Michael's age now + 3 = 2(Alison's age now + 3).
Michael's age now + 3 = 2 × Alison's age now + 6
Michael's age now = 2 Alison's age now + 6 − 3
Michael's age now = 2 Alison's age now + 3.

This is option d.

For example, if Alison is twenty-nine, Michael is 2 × 29 + 3 = 61. So in 3 years' time Alison will be thirty-two and Michael sixty-four, which is double Alison's age.

Solution (substituting values)

Question 3