If the circumference of a circle is 31.4 cm, what is the radius?

Practice Questions

Q1
If the circumference of a circle is 31.4 cm, what is the radius?
  1. 5 cm
  2. 10 cm
  3. 15 cm
  4. 20 cm

Questions & Step-by-Step Solutions

If the circumference of a circle is 31.4 cm, what is the radius?
  • Step 1: Understand that the circumference (C) of a circle is given by the formula C = 2πr, where r is the radius.
  • Step 2: We know the circumference is 31.4 cm, so we can write the equation as 31.4 = 2πr.
  • Step 3: To find the radius (r), we need to rearrange the formula. We can do this by dividing both sides by 2π.
  • Step 4: The formula for the radius becomes r = C / (2π).
  • Step 5: Substitute the value of C (31.4 cm) into the formula: r = 31.4 / (2 * π).
  • Step 6: Use the approximate value of π (3.14) to calculate: r = 31.4 / (2 * 3.14).
  • Step 7: Calculate 2 * 3.14, which equals 6.28.
  • Step 8: Now divide 31.4 by 6.28 to find the radius: r = 31.4 / 6.28.
  • Step 9: Perform the division: r = 5 cm.
  • Circumference of a Circle – The circumference (C) of a circle is calculated using the formula C = 2πr, where r is the radius.
  • Solving for Radius – To find the radius from the circumference, rearranging the formula to r = C/(2π) is necessary.
  • Use of π – Understanding that π can be approximated as 3.14 for calculations.
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