Number · Integers, powers & roots
Chapter 1 · 3
The idea
Factors, multiples and prime numbers
What a factor and a multiple are and how to keep them the right way round, how to list every factor of a number in pairs, why 1 is not prime and 2 is the only even prime, the primes up to 50, square and cube numbers on sight, and how one counter-example settles an "Is she correct?" question.
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Number · Integers, powers & roots
Factors, multiples and prime numbers
What a factor and a multiple are and how to keep them the right way round, how to list every factor of a number in pairs, why 1 is not prime and 2 is the only even prime, the primes up to 50, square and cube numbers on sight, and how one counter-example settles an "Is she correct?" question.
Why it works
Factors: every way to make a rectangle
You have square tiles. You want to lay all of them as one rectangle, with no gaps and no tiles left over. How many different rectangles can you make?Try rows: , so rows of works. Try rows: remainder , so tiles are left over. Five rows fails.
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The rest of the explanation, plus 4 worked examples you step through move by move.
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