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## 'Think of Two Numbers' printed from http://nrich.maths.org/

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

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?

Choose some different pairs of numbers and repeat the process.

Can you figure out how the trick works?

Click here for a poster of this problem.