Choose a starting number from a 1-100 square and cross it out.
Then choose a factor or multiple of that number.
Keep crossing out factors or multiples of the last number in the chain.
For example, Charlie started with 60, 30, 6, 96, 16, 32, 8, 56, 7, 21, 42,...
What's the longest chain you can make?
You may wish to download a 1-100 square to work on, or you could use the interactivity below.