Area of a circle

Difficulty Stretch · Set e53w2c

Take π as 3.14 and give the answer to two decimal places. 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
What is the area, in square mm?
2
What is the area, in square cm?
3
What is the area, in square m?
4
What is the area, in square m?
5
What is the area, in square m?
6
What is the area, in square mm?
7
What is the area, in square mm?
8
What is the area, in square m?
9
What is the area, in square cm?
10
What is the area, in square mm?
11
What is the area, in square m?
12
What is the area, in square m?
13
What is the area, in square m?
14
What is the area, in square m?
15
What is the area, in square mm?
16
What is the area, in square mm?
17
What is the area, in square mm?
18
What is the area, in square m?
19
What is the area, in square mm?
20
What is the area, in square mm?

What is in this set

The numbers in this set run from 2 to 40.
A careful solution takes 2 written steps on average.
The mistake this set invites most often, in 98% of the problems: the radius was doubled — that gives the circumference; the area is π × r × r.
Answers are a decimal.

Drawing 240 problems from this page produced 102 different ones, 43% — 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 7 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.