2 ? 6 ? ? 10 ? ? ? 16

6 ? 12 ? ? 17 ? ? 22 ?

5 ? ? 12 ? ? 19 ? ? 24

? 10 ? 16 ? ? 20 ? ? 27

2 ? ? 9 ? ? 14 ? ? 25

I've worked out the first one is when you cross off all the prime numbers, the remaining numbers go into the missing spaces. This homework was given to my 6 year old nephew, the teacher did not show him how to do it and he has not learnt about prime numbers yet. I think the teacher has given it to him by mistake but none of us can work out what the missing numbers are.

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