A missing side, from the area

Difficulty Stretch · Set 9gnlu9

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 100 square cm. How long is the side marked ?
2
The rectangle has an area of 114 square mm. How long is the side marked ?
3
The rectangle has an area of 864 square m. How long is the side marked ?
4
The rectangle has an area of 1280 square mm. How long is the side marked ?
5
The rectangle has an area of 20 square mm. How long is the side marked ?
6
The rectangle has an area of 8 square mm. How long is the side marked ?
7
The rectangle has an area of 390 square mm. How long is the side marked ?
8
The rectangle has an area of 342 square m. How long is the side marked ?
9
The rectangle has an area of 138 square cm. How long is the side marked ?
10
The rectangle has an area of 319 square m. How long is the side marked ?
11
The rectangle has an area of 170 square m. How long is the side marked ?
12
The rectangle has an area of 624 square cm. How long is the side marked ?
13
The rectangle has an area of 288 square cm. How long is the side marked ?
14
The rectangle has an area of 540 square mm. How long is the side marked ?
15
The rectangle has an area of 1036 square mm. How long is the side marked ?
16
The rectangle has an area of 128 square mm. How long is the side marked ?
17
The rectangle has an area of 360 square m. How long is the side marked ?
18
The rectangle has an area of 546 square mm. How long is the side marked ?
19
The rectangle has an area of 252 square m. How long is the side marked ?
20
The rectangle has an area of 666 square cm. How long is the side marked ?

What is in this set

The numbers in this set run from 3 to 1,521.
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 237 different ones, 99% — 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 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.