Volume of a cylinder, step by step
A cylinder is a circle with height.
The question
A cylinder marked 14 cm, 5 cm tall
14 ÷ 2 =7
base × height
base:3.14 × 7 × 7 =153.86
base:153.86
153.86 × 5 =769.3
- The 14 cm goes right across, so it is the diameter. Halve it first: the radius is 7. Every one of these formulas SQUARES the radius, so getting this wrong is out by a factor of four, not two.
- Same idea as a box: the area of the base times how tall it is. Here the base is a circle, and that is the only difference.
- The circle's area is π × r × r = 3.14 × 7 × 7 = 153.86 square cm.
- Times the height: 153.86 × 5 = 769.3 cubic cm.
How it works.
- 01
The 14 cm goes right across, so it is the diameter. Halve it first: the radius is 7. Every one of these formulas SQUARES the radius, so getting this wrong is out by a factor of four, not two.
- 02
Same idea as a box: the area of the base times how tall it is. Here the base is a circle, and that is the only difference.
- 03
The circle's area is π × r × r = 3.14 × 7 × 7 = 153.86 square cm.
- 04
Times the height: 153.86 × 5 = 769.3 cubic cm.