Step by step
The question
Question: find the volume of a cylinder with diameter 4 m and height 10 m.
1 Find the radius
The diameter goes all the way across the circle.
The radius is half of it.
Half of 4 is 4 divided by 2.
r = 42
4 divided by 2 is 2.
So r = 2 m.
r = 2 m
2 Circle times height
The top is a circle.
Its area is π × r².
The cylinder is that circle, stacked up 10 m high.
π is a special number for circles.
It is about 3.14.
So the volume is V = π × r² × h.
V = π × r2 × h
Now put the numbers in: r = 2 and h = 10.
V = π × 22 × 10
2² means 2 times 2.
That is 4.
22 = 2 × 2 = 4
So V = π × 4 × 10.
V = π × 4 × 10
4 times 10 is 40.
So V = 40π.
We keep π in the answer.
That is the exact answer.
V = 40π m3
3 About how much
To see about how much, put 3.14 for π.
V ≈ 40 × 3.14
40 times 3.14 is 125.6.
So the volume is about 125.6 m³.
V ≈ 125.6 m3
Let's look back.
First: find the radius.
Then: circle times height.
Last: about how much.
Answer
V ≈ 125.6 m3