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Big Blackboard

Age 11 to 14 Short
Challenge Level

The whole numbers from 1 to 2016 are written on a blackboard.

Moritz underlines all the multiples of two in red, all the multiples of three in blue, and all the multiples of four in green.

How many numbers does Moritz underline exactly twice?





This problem is taken from the UKMT Mathematical Challenges.
You can find more short problems, arranged by curriculum topic, in our short problems collection.
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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