Challenge Level

This challenge is about adding and subtracting two-digit numbers.

Pick two two-digit numbers.

Find the sum of the numbers.

Find the difference between the numbers.

Then find the sum and difference of the sum and difference.

What do you notice about the numbers?

Does this always happen?

Try for other starting numbers.

For example:

My numbers are 24 and 31.

The sum of them is 55 and the difference between them is 7.

Now my numbers are 55 and 7.

The sum of them is 62 and the difference between them is 48.

Pick two two-digit numbers.

Find the sum of the numbers.

Find the difference between the numbers.

Then find the sum and difference of the sum and difference.

What do you notice about the numbers?

Does this always happen?

Try for other starting numbers.

For example:

My numbers are 24 and 31.

The sum of them is 55 and the difference between them is 7.

Now my numbers are 55 and 7.

The sum of them is 62 and the difference between them is 48.