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What are the possible ways of making the numbers on the envelopes?
Which number has the fewest possible combinations? It might be worth starting from this envelope and looking at what could be in the others.
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
Roll two red dice and a green dice. Add the two numbers on the red dice and take away the number on the green. What are all the different possible answers?