Math Problem Statement

The diagram shows a semicircle cut from a quarter circle. Find the shaded area. Give your answer correct to 1 decimal place.

Solution

The problem provided is asking to find the shaded area, which is the difference between the area of a quarter circle and the area of a semicircle. Here’s how to solve it step by step:

  1. Quarter Circle: The radius of the quarter circle is the full length of 7 meters.

    The area of a full circle is given by: Acircle=πr2A_{\text{circle}} = \pi r^2 The area of a quarter circle is then: Aquarter circle=14πr2=14π(7)2=494πA_{\text{quarter circle}} = \frac{1}{4} \pi r^2 = \frac{1}{4} \pi (7)^2 = \frac{49}{4} \pi

  2. Semicircle: The diameter of the semicircle is 7 meters, so the radius is half of that: rsemicircle=72=3.5metersr_{\text{semicircle}} = \frac{7}{2} = 3.5 \, \text{meters} The area of a semicircle is: Asemicircle=12πr2=12π(3.5)2=12π(12.25)=6.125πA_{\text{semicircle}} = \frac{1}{2} \pi r^2 = \frac{1}{2} \pi (3.5)^2 = \frac{1}{2} \pi (12.25) = 6.125 \pi

  3. Shaded Area: The shaded area is the difference between the area of the quarter circle and the area of the semicircle: Ashaded=Aquarter circleAsemicircle=494π6.125πA_{\text{shaded}} = A_{\text{quarter circle}} - A_{\text{semicircle}} = \frac{49}{4} \pi - 6.125 \pi Simplifying: Ashaded=(4946.125)πA_{\text{shaded}} = \left( \frac{49}{4} - 6.125 \right) \pi

Now, let’s calculate this value.The shaded area is approximately 19.2 m².

Would you like more details or have any questions? Here are some related questions for deeper understanding:

  1. How do you calculate the area of a sector of a circle with any angle?
  2. What is the formula for finding the area of an arc segment?
  3. How do you find the perimeter of a sector or segment in a circle?
  4. What is the significance of the radius in determining the area of circular shapes?
  5. How do you convert between radians and degrees when working with sectors of a circle?

Tip: When dealing with circular areas, always remember that the area scales with the square of the radius, so doubling the radius will quadruple the area!

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Math Problem Analysis

Mathematical Concepts

Geometry
Area of Circles and Sectors

Formulas

Area of a circle: A = πr²
Area of a quarter circle: A = (1/4)πr²
Area of a semicircle: A = (1/2)πr²

Theorems

Circle Area Theorem
Sector Area Theorem

Suitable Grade Level

Grades 9-10