In a circle, if the radius is increased by 50%, what happens to the area?

Practice Questions

Q1
In a circle, if the radius is increased by 50%, what happens to the area?
  1. Increases by 25%
  2. Increases by 50%
  3. Increases by 75%
  4. Increases by 125%

Questions & Step-by-Step Solutions

In a circle, if the radius is increased by 50%, what happens to the area?
  • Step 1: Understand that the radius of a circle is the distance from the center to the edge.
  • Step 2: If the original radius is 'r', increasing it by 50% means the new radius is 1.5 times the original radius. So, new radius = 1.5r.
  • Step 3: The formula for the area of a circle is A = πr². We will use this formula to find the area with the new radius.
  • Step 4: Substitute the new radius (1.5r) into the area formula: A = π(1.5r)².
  • Step 5: Calculate (1.5r)², which is (1.5)² * r² = 2.25 * r².
  • Step 6: Now, substitute this back into the area formula: A = π * 2.25 * r² = 2.25πr².
  • Step 7: Compare the new area (2.25πr²) to the original area (πr²). The original area is πr².
  • Step 8: To find the increase in area, subtract the original area from the new area: 2.25πr² - πr² = 1.25πr².
  • Step 9: To find the percentage increase, divide the increase (1.25πr²) by the original area (πr²): (1.25πr²) / (πr²) = 1.25.
  • Step 10: Convert this to a percentage: 1.25 = 125%. This means the area increases by 125%.
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