List the factors, step by step

Before a child can find a greatest common factor, they need to find factors at all.

Practice Practice sheet New questions

The question

Factors of 16

16

so far:116

so far:12816

so far:124816

so far:124816

Factors come in PAIRS — every one you find hands you a second. So work in from both ends rather than trying every number in turn.
1 × 16 = 16, so 1 and 16 are both factors.
2 × 8 = 16, so 2 and 8 are both factors.
4 × 4 = 16, so 4 pairs with itself — that is the middle, and there is nothing past it.
The pair has met in the middle, so the list is finished: 1, 2, 4, 8, 16. 5 factors.

How it works.

01
Factors come in PAIRS — every one you find hands you a second. So work in from both ends rather than trying every number in turn.
02
1 × 16 = 16, so 1 and 16 are both factors.
03
2 × 8 = 16, so 2 and 8 are both factors.
04
4 × 4 = 16, so 4 pairs with itself — that is the middle, and there is nothing past it.
05
The pair has met in the middle, so the list is finished: 1, 2, 4, 8, 16. 5 factors.