Here's a game to play with an adult!
How do you play?
You'll need an adult to play with. You'll also need a grid of numbers from 1 to 100 (you can print one from here), or you can use the interactive version.
The grown-up chooses a positive even number that is less than 50, and crosses it out on the grid. You then choose another number to cross out. The number must be a factor or multiple of the first number. Take it in turns to cross out numbers, at each stage choosing a number that is a factor or multiple of the number just crossed out by the other player.
The first person who is unable to cross out a number loses. Try playing again with you going first.
Do you have any winning strategies?
Are there any numbers you shouldn't go to?