Highest common factor of two numbers

Difficulty Starter · Set ohqduw

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1
What is the greatest common factor of 23 and 7?
2
What is the greatest common factor of 17 and 10?
3
What is the greatest common factor of 5 and 16?
4
What is the greatest common factor of 22 and 9?
5
What is the greatest common factor of 6 and 15?
6
What is the greatest common factor of 12 and 5?
7
What is the greatest common factor of 13 and 20?
8
What is the greatest common factor of 23 and 14?
9
What is the greatest common factor of 8 and 21?
10
What is the greatest common factor of 12 and 17?
11
What is the greatest common factor of 14 and 6?
12
What is the greatest common factor of 10 and 22?
13
What is the greatest common factor of 15 and 12?
14
What is the greatest common factor of 21 and 12?
15
What is the greatest common factor of 19 and 20?
16
What is the greatest common factor of 13 and 11?
17
What is the greatest common factor of 22 and 24?
18
What is the greatest common factor of 20 and 14?
19
What is the greatest common factor of 16 and 10?
20
What is the greatest common factor of 8 and 5?

What is in this set

The numbers in this set run from 4 to 24.
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 187 different ones, 78% — 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.