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Two Primes Make One Square

Age 7 to 11 Challenge Level:

What are the squares of the numbers from $4$ to $20$?
What happens when you add two prime numbers together?
What happens if you add two different prime numbers 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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