Question

Andrew thinks of a number, adds 9 and multiplies the result by 3. Andrea thinks of a number, multiplies it by 3 and adds 9 to the result. Both Andrew and Andrea get an answer of 60. Did Andrew and Andrea begin by selecting the same number? Show working out to support your answer.

Answer 1

Step-by-step explanation:

Let the number that Andrew thinks be 'x'

When 9 is added, x + 9

When 3 is multiplied, we get 3 * (x + 9) = 3x + 27 = 60  ....   (i)

3x + 27 = 60

3x = 60 - 27

3x = 33

x = 33 ÷ 3

x = 11

The number that Andrew thought  was 11

Let the number that Andrea thinks be 'y'.

When 3 is multiplied, 3y

When 9 is added, 3y + 9 = 60

3y + 9 = 60

3y = 60 - 9

3y = 51

y = 51 ÷ 3

y = 17

The number that Andrea thought  was 17.

So, Andrew and Andrea did not start with the same number.