Aditya from Bristol Grammar School began by saying:

I predicted that the solutions to the five values would be quite similar, for example 61% of 71 is equal to 71% of 61, and this was very similar to '77% of 56' and '7% of 614'. Also, 17% of 253 seems to be quite like 19% of 226.

Well done -- good reasoning. Chris and Elliot from Moorfield Junior School sent us the correct solution but didn't tell us how they did it. Anthony and Azezze at Brookfield Primary have explained their working clearly:

We both worked from the bottom left all the way round to the bottom right.
We worked out those by dividing the number by 100 and multipling the answer by the percentage.

So the answers in that way are:
1. 7% of 614 = 42.98
2. 13% of 330 = 42.9
3. 17% of 253 = 43.01
4. 19% of 226 = 42.94
5. 23% of 187 = 43.01
6. 61% of 71 = 43.31
7. 77% of 56 = 43.12

We found out that the largest ball is number 6 (61% of 71 = 43.31)
We also found out that the smallest is number 2 (13% of 330 = 42.9)
So we took away those numbers and got 0.41.

This is fantastic so far. Just the last step to go!