Penny, Tom and Matthew were each given a box of mint chocolates in a hexagonal box:

Delicious chocolates
Penny ate $10$ chocolates:
When she looked at the remaining chocolates, she quickly worked out that there must have been $61$ chocolates at the start.
Tom ate $20$ chocolates:
He also managed to work out very quickly that there were originally $61$ chocolates.
Matthew ate $24$ chocolates:
He could also see very easily that he must have started with $61$ chocolates.
Penny, Tom and Matthew have been promised a larger box of chocolates as a Christmas present from their grandmother. The box will have $10$ chocolates along each edge, instead of just $5$.
How would each child work out how many chocolates the larger box will contain?
Can you describe any other ways to work it out?
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