If the circumference of a circle is 31.4 cm, what is its radius? (Use π = 3.14)

Practice Questions

Q1
If the circumference of a circle is 31.4 cm, what is its radius? (Use π = 3.14) (2015)
  1. 5 cm
  2. 7 cm
  3. 10 cm
  4. 8 cm

Questions & Step-by-Step Solutions

If the circumference of a circle is 31.4 cm, what is its radius? (Use π = 3.14) (2015)
  • Step 1: Write down the formula for the circumference of a circle, which is Circumference = 2πr.
  • Step 2: We know the circumference is 31.4 cm, so we can set up the equation: 31.4 = 2πr.
  • Step 3: Substitute π with 3.14 in the equation: 31.4 = 2 * 3.14 * r.
  • Step 4: Calculate 2 * 3.14, which equals 6.28. Now the equation is: 31.4 = 6.28r.
  • Step 5: To find r, divide both sides of the equation by 6.28: r = 31.4 / 6.28.
  • Step 6: Calculate 31.4 divided by 6.28, which equals 5. Therefore, the radius r is 5 cm.
  • 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.
  • Use of π – Understanding that π can be approximated as 3.14 for calculations in this context.
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