Highest common factor of two numbers

Difficulty Stretch · Set 5aer9a

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1
What is the greatest common factor of 90 and 22?
2
What is the greatest common factor of 27 and 70?
3
What is the greatest common factor of 115 and 136?
4
What is the greatest common factor of 60 and 39?
5
What is the greatest common factor of 6 and 44?
6
What is the greatest common factor of 53 and 112?
7
What is the greatest common factor of 63 and 126?
8
What is the greatest common factor of 20 and 23?
9
What is the greatest common factor of 23 and 66?
10
What is the greatest common factor of 121 and 82?
11
What is the greatest common factor of 6 and 77?
12
What is the greatest common factor of 122 and 103?
13
What is the greatest common factor of 116 and 103?
14
What is the greatest common factor of 94 and 101?
15
What is the greatest common factor of 4 and 143?
16
What is the greatest common factor of 14 and 49?
17
What is the greatest common factor of 142 and 27?
18
What is the greatest common factor of 103 and 30?
19
What is the greatest common factor of 142 and 27?
20
What is the greatest common factor of 53 and 13?

What is in this set

The numbers in this set run from 4 to 144.
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 239 different ones, 100% — 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.