Math Problem Statement

A rectangular piece of paper with a length of 24 centimeters and a width of 16 centimeters has a semicircle cut out of it. Find the perimeter and area of the remaining shape.

Solution

Let's break down the problem:

We have a rectangular piece of paper with dimensions 24 cm (length) and 16 cm (width), with a semicircle cut out from one side (the shorter side). The objective is to find:

  1. The perimeter of the paper after the semicircle is cut out.
  2. The area of the paper after the semicircle is cut out.

Part a) Finding the Perimeter

  • The perimeter of the rectangle without the cutout would normally be: Perimeter of rectangle=2(length+width)=2(24+16)=80cm\text{Perimeter of rectangle} = 2(\text{length} + \text{width}) = 2(24 + 16) = 80 \, \text{cm}

  • Since a semicircle is cut out, we need to subtract the width of the rectangle that matches the diameter of the semicircle and add the circumference of the semicircle.

  • The diameter of the semicircle is 16 cm (the width of the rectangle), so the radius rr is: r=162=8cmr = \frac{16}{2} = 8 \, \text{cm}

  • The circumference of a full circle is 2πr2\pi r, so the circumference of the semicircle is: Circumference of semicircle=πr=3.14×8=25.12cm\text{Circumference of semicircle} = \pi r = 3.14 \times 8 = 25.12 \, \text{cm}

  • The modified perimeter will be: Perimeter=80cm (original)16cm (width)+25.12cm (semicircle circumference)=89.12cm\text{Perimeter} = 80 \, \text{cm (original)} - 16 \, \text{cm (width)} + 25.12 \, \text{cm (semicircle circumference)} = 89.12 \, \text{cm}

Part b) Finding the Area

  • The area of the rectangle is: Area of rectangle=length×width=24×16=384cm2\text{Area of rectangle} = \text{length} \times \text{width} = 24 \times 16 = 384 \, \text{cm}^2

  • The area of the semicircle is half the area of a full circle: Area of semicircle=12πr2=12×3.14×82=12×3.14×64=100.48cm2\text{Area of semicircle} = \frac{1}{2} \pi r^2 = \frac{1}{2} \times 3.14 \times 8^2 = \frac{1}{2} \times 3.14 \times 64 = 100.48 \, \text{cm}^2

  • The modified area will be: Area=384cm2100.48cm2=283.52cm2\text{Area} = 384 \, \text{cm}^2 - 100.48 \, \text{cm}^2 = 283.52 \, \text{cm}^2

Final Answers:

  • Perimeter = 89.12 cm
  • Area = 283.52 cm²

Let me know if you would like any further clarification or additional details.


Here are 5 related questions you might want to explore:

  1. How would the perimeter change if the semicircle had a different radius?
  2. What is the perimeter if the shape had a full circle instead of a semicircle cut out?
  3. How do the area and perimeter change if the dimensions of the rectangle increase proportionally?
  4. What if the cutout was an equilateral triangle instead of a semicircle?
  5. How would you calculate the perimeter and area if an ellipse was cut out instead of a semicircle?

Tip: Remember, when dealing with circles, always ensure you use the correct approximation for π\pi depending on the precision required (e.g., 3.14, or π\pi in exact terms).

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Math Problem Analysis

Mathematical Concepts

Geometry
Perimeter
Area
Circles and Semicircles

Formulas

Perimeter of a rectangle: 2(length + width)
Circumference of a semicircle: πr
Area of a rectangle: length × width
Area of a semicircle: (1/2)πr^2

Theorems

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Suitable Grade Level

Grades 6-8