Highest common factor of two numbers

Difficulty Standard · Set x82cpo

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1
What is the greatest common factor of 31 and 21?
2
What is the greatest common factor of 24 and 42?
3
What is the greatest common factor of 45 and 17?
4
What is the greatest common factor of 5 and 20?
5
What is the greatest common factor of 8 and 22?
6
What is the greatest common factor of 33 and 26?
7
What is the greatest common factor of 24 and 18?
8
What is the greatest common factor of 41 and 51?
9
What is the greatest common factor of 15 and 34?
10
What is the greatest common factor of 48 and 26?
11
What is the greatest common factor of 43 and 25?
12
What is the greatest common factor of 44 and 23?
13
What is the greatest common factor of 36 and 7?
14
What is the greatest common factor of 34 and 32?
15
What is the greatest common factor of 7 and 11?
16
What is the greatest common factor of 42 and 8?
17
What is the greatest common factor of 45 and 9?
18
What is the greatest common factor of 31 and 8?
19
What is the greatest common factor of 28 and 46?
20
What is the greatest common factor of 11 and 43?

What is in this set

The numbers in this set run from 4 to 60.
62% of them share no factor at all.
38% of them share a factor.
A careful solution takes 3 written steps on average.
The mistake this set invites most often, in 100% of the problems: that is the least common multiple — the greatest common factor is never larger than either number.
Answers are a whole number.

Drawing 240 problems from this page produced 232 different ones, 97% — so a sheet of 20 is a new sheet almost every time.

The same skill, harder or easier

We would put this in front of a grade 6 class. That is our judgement, not a standard, and it is printed here so you can disagree with it. Everything else we put in that year.