Pi (π) Math Example 2

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Example 2

medium
A circle has a radius of 7 m. Find its area. Use π≈3.14\pi \approx 3.14.

Solution

  1. 1
    Step 1: The formula for the area of a circle is A=πr2A = \pi r^2.
  2. 2
    Step 2: The radius is r=7r = 7 m, so r2=49r^2 = 49 m².
  3. 3
    Step 3: Multiply: A=3.14×49=153.86A = 3.14 \times 49 = 153.86 m².
  4. 4
    Step 4: Round if needed: A≈153.86A \approx 153.86 m².

Answer

A≈153.86A \approx 153.86 m²
The area formula A=πr2A = \pi r^2 comes from integrating the circumference formula. Every additional ring of width drdr at radius rr adds area 2πr dr2\pi r\,dr; integrating from 0 to RR gives πR2\pi R^2.

About Pi (π)

The ratio of a circle's circumference to its diameter, approximately 3.14159…3.14159\ldots

Learn more about Pi (π) →

More Pi (π) Examples

Example 1 easy

A circle has a diameter of 10 cm. What is its circumference? Use [formula].

Example 3 medium

A circular pool has a circumference of 31.4 m. Find its radius and area. Use [formula].

Example 4 easy

A circle's circumference is [formula] cm. What is its diameter? Use [formula].

Example 5 hard

A wheel of radius 0.5 m rolls without slipping. How many full rotations does it make to travel 100 m

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