Here’s a classic puzzle you should try with your child:
My uncle was 31 when I was 8. Now he is twice as old as I am. How old am I?
Here’s a Solution:
First find the difference in ages. It is 31 – 8 = 23.
The difference in ages does not change with time, of course. My uncle will always be 23 years older. So if my uncle is twice as old, I must be 23.
Elegant solution for a problem that might be hard to solve at first.