Math Problem Statement

Jared has a circular piece of paper with a radius of 11 cm. He cuts a circular hole with a radius of 5 cm in the center of his piece of paper to make the shape shown. Calculate the area of this shape. Give your answer in cm² to 1 d.p.

Solution

To calculate the area of the shape shown (a circular piece of paper with a smaller circular hole cut out), we need to:

  1. Find the area of the larger circle (radius = 11 cm).
  2. Find the area of the smaller circle (radius = 5 cm).
  3. Subtract the area of the smaller circle from the area of the larger circle to get the area of the shape.

Step 1: Area of the larger circle

The formula for the area of a circle is: A=πr2A = \pi r^2 For the larger circle, r=11cmr = 11 \, \text{cm}: Alarge=π×112=π×121380.13cm2A_{\text{large}} = \pi \times 11^2 = \pi \times 121 \approx 380.13 \, \text{cm}^2

Step 2: Area of the smaller circle

For the smaller circle, r=5cmr = 5 \, \text{cm}: Asmall=π×52=π×2578.54cm2A_{\text{small}} = \pi \times 5^2 = \pi \times 25 \approx 78.54 \, \text{cm}^2

Step 3: Subtract the areas

Now subtract the area of the smaller circle from the area of the larger circle: Area of the shape=380.1378.54=301.59cm2\text{Area of the shape} = 380.13 - 78.54 = 301.59 \, \text{cm}^2

Final Answer

The area of the shape is approximately 301.6 cm² (rounded to 1 decimal place).

Do you want further details or have any questions?

Here are 5 related questions:

  1. What would be the area if the radius of the hole was 7 cm instead?
  2. How does changing the radius of the larger circle affect the final area?
  3. How can you calculate the circumference of both circles?
  4. What is the relationship between the area and the radius in a circle?
  5. Can you calculate the area of a sector of the larger circle if part of it was cut out?

Tip: Always remember to subtract the area of the smaller circle from the larger one when dealing with ring-like shapes (annuli).

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Math Problem Analysis

Mathematical Concepts

Geometry
Circle Area

Formulas

Area of a circle = πr²

Theorems

Area subtraction theorem (difference of areas)

Suitable Grade Level

Grade 8-10