Imagine you have four bags containing a large number of 1s, 4s, 7s and 10s.

You can choose numbers from the bags and add them┬áto make different totals. You don’t have to use numbers from every bag, and there will always be as many of each number as you need.

Choose some sets of 3 numbers and add them together.

What is special about your answers?
Can you explain what you’ve noticed?

Click here to download Notes for Teachers.

Thank you to NRICH for this problem.


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