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Arti wrote to us to say:

There are two things that are not defined which need a definition:
- If player A marked a number in the number line, can player B mark it later?
- If player A used two numbers from the square, can player B use one or both those numbers?

These are good questions, Arti.  What did you decide in the game/s you played?  Did that work well?  You could try out both versions and decide which works better.

Rowena from Christ Church Primary told us:

I played this game with my Mum and neither of us won. We played it again and my Mum let me win!
We decided to list all the possible whole number answers. They were 2, 3, 4, 5, 6, 8, 9, 10, 12, 15 and 20. Once we knew these, it was easy to choose numbers to block the opponent and not let them get four in a row.
You can only win if your opponent makes a mistake or lets you win!
 

Thank you, Rowena - that was a good idea to make a list of the whole number answers.

I wonder whether you could change the game to make it a better game?