Lottie and Adele sent us a great solution to this problem. They answer each part in turn and explain clearly as they go along:
1. To make it balance with 10 on one side, using only one hook, you can put two on the 5 or one on the 10 or five on number 2 or ten on 1.
2. Two weights on the 10=20. So put ten on number 2 hook to make it balance.
3. You could put four weights on the 5 to make it balance with 20 (2 10s).
4. You can put two on the 5 or put five weights on the 2. There is only one solution.
5. It balances by putting one on the 7 (with the 3) and the 10 on the other side.
Thank you to you both. I wonder if there are other ways of making it balance if you have one weight on the 10 hook on one side and can use the 3 hook and one other hook on the other side? Don't forget that you can have more than one weight on a hook.