Math Problem Statement

Calculate the area of this shaded region if PQ, QR, and RS are diameters with SR = 4, RQ = 2SR, QP = 2RQ.

Solution

In this image, we are tasked with calculating the area of a shaded region consisting of semicircles and a full circle, where the diameters of the semicircles are given in relation to one another. Let's break down the problem step by step:

Given Information:

  • SR=4SR = 4 (The diameter of the smallest semicircle)
  • RQ=2×SR=8RQ = 2 \times SR = 8 (The diameter of the middle semicircle)
  • QP=2×RQ=16QP = 2 \times RQ = 16 (The diameter of the largest semicircle)

Step 1: Understanding the geometry

  • The shaded region is made of three semicircles with diameters SR=4SR = 4, RQ=8RQ = 8, and QP=16QP = 16.
  • These semicircles are aligned in such a way that they form a figure with one large semicircle and two smaller ones inside.

Step 2: Calculating the area of the semicircles

The formula for the area of a semicircle is given by:

Asemicircle=12πr2A_{\text{semicircle}} = \frac{1}{2} \pi r^2

where rr is the radius, which is half of the diameter.

  • For the largest semicircle (diameter 1616): r1=162=8A1=12π(8)2=12π×64=32πr_1 = \frac{16}{2} = 8 \quad \Rightarrow \quad A_1 = \frac{1}{2} \pi (8)^2 = \frac{1}{2} \pi \times 64 = 32\pi

  • For the middle semicircle (diameter 88): r2=82=4A2=12π(4)2=12π×16=8πr_2 = \frac{8}{2} = 4 \quad \Rightarrow \quad A_2 = \frac{1}{2} \pi (4)^2 = \frac{1}{2} \pi \times 16 = 8\pi

  • For the smallest semicircle (diameter 44): r3=42=2A3=12π(2)2=12π×4=2πr_3 = \frac{4}{2} = 2 \quad \Rightarrow \quad A_3 = \frac{1}{2} \pi (2)^2 = \frac{1}{2} \pi \times 4 = 2\pi

Step 3: Calculating the total shaded area

The shaded area consists of the largest semicircle minus the two smaller semicircles.

Shaded Area=A1(A2+A3)=32π(8π+2π)=32π10π=22π\text{Shaded Area} = A_1 - (A_2 + A_3) = 32\pi - (8\pi + 2\pi) = 32\pi - 10\pi = 22\pi

Thus, the area of the shaded region is:

22π\boxed{22\pi}

Do you need further clarification or additional details?


Here are 5 related questions:

  1. What is the formula for the area of a full circle instead of a semicircle?
  2. How would the solution change if the figures were full circles instead of semicircles?
  3. Can you find the circumference of each semicircle using their radii?
  4. How would you calculate the perimeter of the shaded region?
  5. How would the area change if the diameter of the largest semicircle were doubled?

Tip:

When dealing with composite shapes, breaking them into simpler geometric figures can make complex area calculations much easier!

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Math Problem Analysis

Mathematical Concepts

Geometry
Circles
Area of Semicircles
Composite Figures

Formulas

Area of a semicircle: A = 1/2 * π * r^2
Radius of a circle: r = diameter / 2

Theorems

Area calculation for semicircles and composite shapes

Suitable Grade Level

Grades 8-10