If the radius of a circle is decreased by 2 cm, how does the area change? (Origi

Practice Questions

Q1
If the radius of a circle is decreased by 2 cm, how does the area change? (Original radius is 10 cm) (2021)
  1. Decreases by 12.56 cm²
  2. Decreases by 25.12 cm²
  3. Decreases by 31.4 cm²
  4. Decreases by 50.24 cm²

Questions & Step-by-Step Solutions

If the radius of a circle is decreased by 2 cm, how does the area change? (Original radius is 10 cm) (2021)
  • Step 1: Identify the original radius of the circle, which is 10 cm.
  • Step 2: Calculate the original area using the formula for the area of a circle: Area = π * (radius)². So, Area = π * (10)².
  • Step 3: Calculate (10)², which is 100.
  • Step 4: Multiply 100 by π (approximately 3.14) to find the original area. So, Original Area = 3.14 * 100 = 314 cm².
  • Step 5: Identify the new radius after decreasing by 2 cm. New radius = 10 cm - 2 cm = 8 cm.
  • Step 6: Calculate the new area using the same formula: Area = π * (8)².
  • Step 7: Calculate (8)², which is 64.
  • Step 8: Multiply 64 by π (approximately 3.14) to find the new area. So, New Area = 3.14 * 64 = 201.06 cm².
  • Step 9: Find the change in area by subtracting the new area from the original area. Change = Original Area - New Area.
  • Step 10: Calculate the change: 314 cm² - 201.06 cm² = 112.94 cm².
  • Area of a Circle – Understanding how to calculate the area of a circle using the formula A = πr² and how changes in the radius affect the area.
  • Impact of Radius Change – Analyzing how a decrease in radius impacts the overall area, emphasizing the quadratic relationship between radius and area.
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