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# Pair Sums

**What are the five numbers?**## Related Collections

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### Consecutive Numbers

### Adding All Nine

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Age 11 to 14

Challenge Level

- Problem
- Student Solutions

Five numbers are added together in pairs to produce the following answers:

$0, 2, 4, 4, 6, 8, 9, 11, 13, 15$

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

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!