Factors, multiples and primes
Arrange counters into rectangles to find a number's factors. See why some numbers make only one rectangle.
- UK: Year 4
- France: grade 3
- Germany: grade 3
- Iran: grade 7
- Afghanistan: grade 5
- Syria: grade 4
- Palestine: grade 4
- Ukraine: grade 6
- Russia: grade 5
Guide
This studio covers Year 4–6 work on factors, multiples and primes. The number of counters stays the same and only the row length changes. If the row length is not a factor (divisor of a number) of the number, the last row is short.
Each rectangle is a factor pair: 12 = 3 × 4 means 3 and 4 are factors of 12, and 12 is a multiple of 3 and of 4. A number with exactly two factors (1 and itself) is a prime number; the others are composite. 1 is neither prime nor composite.
In the last mission a factor tree breaks a number down until every branch ends in a prime (prime factorisation). Common slips: forgetting 1 and the number itself, counting pairs instead of factors, and thinking every odd number (like 9) is prime.