A circle has a circumference of 31.4 cm. What is the radius of the circle?

Practice Questions

Q1
A circle has a circumference of 31.4 cm. What is the radius of the circle?
  1. 5 cm
  2. 10 cm
  3. 7 cm
  4. 15 cm

Questions & Step-by-Step Solutions

A circle has a circumference of 31.4 cm. What is the radius of the circle?
  • Step 1: Understand that the circumference of a circle is given by the formula C = 2πr, where C is the circumference and r is the radius.
  • Step 2: We know the circumference (C) is 31.4 cm. So we can write the equation: 31.4 = 2πr.
  • Step 3: To find the radius (r), we need to isolate r in the equation. First, divide both sides of the equation by 2π: r = 31.4 / (2π).
  • Step 4: Now, calculate the value of r. Use the approximate value of π (3.14) for easier calculation: r = 31.4 / (2 * 3.14).
  • Step 5: Calculate 2 * 3.14, which equals 6.28. Now divide 31.4 by 6.28: r = 31.4 / 6.28.
  • Step 6: Perform the division: r = 5 cm. This is the radius of the circle.
  • Circumference of a Circle – The circumference of a circle is calculated using the formula C = 2πr, where C is the circumference and r is the radius.
  • Solving for Radius – To find the radius from the circumference, rearranging the formula to r = C/(2π) is necessary.
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