Question

Here's a math trick to try:
Think of one of the numbers from 1 to 9.
Add 9 to your number.
Add the digits of your answer together. What is your new number?
What do you notice?

Try the trick again with a new starting number. What do you notice now?

Jonas tried the trick with a few different numbers. He said:

I think you will always get back to your original number, because adding 9 is the same as adding 10 and subtracting 1.

Can you help him explain what's happening?

Answer 1

Answer: we just add a zero to the one

Explanation: which is like magic by the way.

Hope it helps you.