Area of a Circle Math Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
Find the area of a semicircle with diameter 2020 cm. Give your answer to one decimal place.

Solution

  1. 1
    First find the radius: r=202=10r = \frac{20}{2} = 10 cm.
  2. 2
    Area of the full circle: A=ฯ€(10)2=100ฯ€A = \pi (10)^2 = 100\pi.
  3. 3
    Area of the semicircle: A=100ฯ€2=50ฯ€โ‰ˆ157.1A = \frac{100\pi}{2} = 50\pi \approx 157.1 cmยฒ.

Answer

Aโ‰ˆ157.1ย cm2A \approx 157.1 \text{ cm}^2
A semicircle is half a circle, so halve the full circle area. Always convert diameter to radius before using A=ฯ€r2A = \pi r^2.

About Area of a Circle

The amount of space enclosed inside a circle, calculated as ฯ€\pi times the square of the radius.

Learn more about Area of a Circle โ†’

More Area of a Circle Examples

Example 1 easy

Find the area of a circle with radius [formula] cm. Leave your answer in terms of [formula].

Example 3 hard

A circular garden has an area of [formula] mยฒ. Find the radius of the garden. Use [formula].

Example 4 medium

A circular pond has radius [formula] m. A path around it extends the outer radius to [formula] m. Fi

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