A missing side, from the area

Difficulty Starter · Set njhe5r

The drawings are schematic: work from the lengths marked on them, not from their proportions.

Fill in what you can and press Check. Nothing you type is sent anywhere.

1
The rectangle has an area of 45 square mm. How long is the side marked ?
2
The rectangle has an area of 48 square mm. How long is the side marked ?
3
The rectangle has an area of 36 square cm. How long is the side marked ?
4
The rectangle has an area of 42 square mm. How long is the side marked ?
5
The rectangle has an area of 30 square mm. How long is the side marked ?
6
The rectangle has an area of 15 square cm. How long is the side marked ?
7
The rectangle has an area of 6 square m. How long is the side marked ?
8
The rectangle has an area of 30 square mm. How long is the side marked ?
9
The rectangle has an area of 21 square mm. How long is the side marked ?
10
The rectangle has an area of 18 square m. How long is the side marked ?
11
The rectangle has an area of 12 square m. How long is the side marked ?
12
The rectangle has an area of 40 square cm. How long is the side marked ?
13
The rectangle has an area of 42 square mm. How long is the side marked ?
14
The rectangle has an area of 24 square m. How long is the side marked ?
15
The rectangle has an area of 42 square m. How long is the side marked ?
16
The rectangle has an area of 32 square m. How long is the side marked ?
17
The rectangle has an area of 30 square cm. How long is the side marked ?
18
The rectangle has an area of 20 square mm. How long is the side marked ?
19
The rectangle has an area of 16 square m. How long is the side marked ?
20
The rectangle has an area of 25 square mm. How long is the side marked ?

What is in this set

The numbers in this set run from 3 to 81.
Every problem in it will run the formula backwards.
A careful solution takes 2 written steps on average.
The mistake this set invites most often, in 100% of the problems: the width was taken away from the area.
Answers are a whole number.

Drawing 240 problems from this page produced 122 different ones, 51% — so a sheet of 20 will come back to a problem you have seen — there are only so many sensible ones of this kind.

The same skill, harder or easier

We would put this in front of a grade 5 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.