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# Puzzles

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## Blackboard Sums

The numbers 1 to 20 are written on a blackboard. Each turn, you may erase two numbers, $$a$$ and $$b$$ and write the sum $$a+b$$ in their place. You continue until only one number remains.
What is the largest number you can make?
Tags: numbers
If you enjoyed this puzzle, check out Sunday Afternoon Maths LXII,
puzzles about division, or a random puzzle.