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Adding All Nine

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Counting Factors

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Hot Pursuit

Age 11 to 14 Challenge Level:

I added together the first 'n' natural numbers (positive integers) and was surprised to notice that my answer was a 3 digit number in which all the digits were the same.

How many numbers did I add together?

The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.
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