Think of Two Numbers

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Here is an alternative and more unusual version of the "Think of a Number" game which you may have heard of before.

numbers 0-9

Think of two whole numbers under $10$.
Take one of them and add $1$.
Multiply by $5$.
Add $1$ again.
Double your answer.
Subtract $1$.
Add your second number.
Add $2$.
Double again.
Subtract $8$.
Halve this number and tell me your answer.

From your answer I can work out both your numbers very quickly. How?

Try with different numbers until you see how it works and then you'll be ready to amaze your friends!

A poster of this problem is available here.


Published May 2003.