Step by step
The question
Question: find the area of a circle with radius 1.5 m.
1 Use the rule
π is a special number for circles.
It is about 3.14.
The area of a circle is π times the radius squared: A = π × r².
So we write A = π × r².
Now put the numbers in: r = 1.5.
1.5² means 1.5 times 1.5.
Forget the points: 15 times 15 is 225.
Together, the numbers have 1 + 1 = 2 digits after the point.
So the answer has 2 too: 2.25.
So A = π × 2.25.
We write it as 2.25π.
We keep π in the answer.
That is the exact answer.
2 About how much
To see about how much, put 3.14 for π.
Forget the points: 225 times 314 is 70650.
Together, the numbers have 2 + 2 = 4 digits after the point.
So the answer has 4 too: 7.0650, which is 7.065.
That is 7.065.
Rounded to 2 decimal places, it is 7.07.
So the area is about 7.07 m².
Let's look back.
First: use the rule.
Last: about how much.