Find a cylinder’s exact volume
The idea
The base area is πr2; r is the radius, not the diameter.
Step by step
- The base area is πr2; r is the radius, not the diameter.
- A right cylinder has volume base area × height, so V = πr2h.
- Keep π for an exact result and use cubic units.
Example
A cylinder has radius 2 cm and height 3 cm. What is its exact volume?
Answer
12π cm3
The circular base has area πr2 = 4π cm2. Multiply by height: 4π × 3 = 12π cm3.
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Sketch a cylinder with radius 2 units and height 5 units. Explain why its volume is 20π cubic units, not 10π.
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