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Consecutive Numbers

An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.

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Adding All Nine

Make a set of numbers that use all the digits from 1 to 9, once and once only. Add them up. The result is divisible by 9. Add each of the digits in the new number. What is their sum? Now try some other possibilities for yourself!


Age 11 to 14
Challenge Level


Try to think about the biggest or smallest numbers you could add together in each case.

Does that tell you anything about the digits of the number that they sum to ?

If you add two $2$ digit numbers together to make a $3$ digit number, what could the first digit of the answer be?