The missing numerator in an equivalent fraction

Difficulty Stretch · Set kh4iko

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1
718=?90— what is the numerator?
2
16=?24— what is the numerator?
3
211=?44— what is the numerator?
4
17=?14— what is the numerator?
5
1213=?26— what is the numerator?
6
12=?6— what is the numerator?
7
417=?68— what is the numerator?
8
1920=?80— what is the numerator?
9
45=?10— what is the numerator?
10
619=?76— what is the numerator?
11
12=?12— what is the numerator?
12
15=?15— what is the numerator?
13
14=?12— what is the numerator?
14
25=?25— what is the numerator?
15
14=?16— what is the numerator?
16
1213=?65— what is the numerator?
17
419=?38— what is the numerator?
18
25=?15— what is the numerator?
19
517=?34— what is the numerator?
20
1517=?68— what is the numerator?

What is in this set

The numbers in this set run from 1 to 120.
A careful solution takes 2 written steps on average.
The mistake this set invites most often, in 100% of the problems: the denominator grew by 8 and the same amount was added on top.
Answers are a whole number.

Drawing 240 problems from this page produced 185 different ones, 77% — 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 4 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.