Math Problem Statement

For the figures below, assume they are made of semicircles, quarter circles, and squares. For each shape, find the area and perimeter. Give your answer as a completely simplified exact value in terms of π (no approximations).

Solution

The given figure is composed of a right triangle and a quarter circle. Let us calculate its area and perimeter step by step.

Given:

  • The base AB=6cmAB = 6 \, \text{cm}, and the quarter circle is based on this diameter.
  • ACAC is the hypotenuse of the triangle, while BCBC is the height of the triangle.

Step 1: Area

(a) Area of the right triangle (ABC\triangle ABC):

Using the formula for the area of a triangle: Area of ABC=12×base×height.\text{Area of } \triangle ABC = \frac{1}{2} \times \text{base} \times \text{height}.

The base AB=6cmAB = 6 \, \text{cm} and the height BC=6cmBC = 6 \, \text{cm} (since the quarter circle's radius equals the height): Area of ABC=12×6×6=18cm2.\text{Area of } \triangle ABC = \frac{1}{2} \times 6 \times 6 = 18 \, \text{cm}^2.


(b) Area of the quarter circle:

The formula for the area of a quarter circle is: Area of a quarter circle=14πr2,\text{Area of a quarter circle} = \frac{1}{4} \pi r^2, where rr is the radius. The radius of the quarter circle is: r=diameter2=62=3cm.r = \frac{\text{diameter}}{2} = \frac{6}{2} = 3 \, \text{cm}.

Substituting r=3r = 3: Area of quarter circle=14π(3)2=9π4cm2.\text{Area of quarter circle} = \frac{1}{4} \pi (3)^2 = \frac{9\pi}{4} \, \text{cm}^2.


Total Area:

Total Area=Area of triangle+Area of quarter circle.\text{Total Area} = \text{Area of triangle} + \text{Area of quarter circle}. Total Area=18+9π4.\text{Total Area} = 18 + \frac{9\pi}{4}.

So, the total area is: Total Area=18+9π4cm2.\boxed{\text{Total Area} = 18 + \frac{9\pi}{4} \, \text{cm}^2}.


Step 2: Perimeter

The perimeter consists of:

  1. The hypotenuse (ACAC),
  2. The curved edge of the quarter circle,
  3. The straight side (BCBC).

(a) Length of ACAC (Hypotenuse):

Using the Pythagorean theorem: AC=AB2+BC2=62+62=72=62cm.AC = \sqrt{AB^2 + BC^2} = \sqrt{6^2 + 6^2} = \sqrt{72} = 6\sqrt{2} \, \text{cm}.


(b) Length of the quarter-circle arc:

The formula for the arc length of a quarter circle is: Arc length=14×2πr=πr2.\text{Arc length} = \frac{1}{4} \times 2\pi r = \frac{\pi r}{2}. With r=3cmr = 3 \, \text{cm}: Arc length=π(3)2=3π2cm.\text{Arc length} = \frac{\pi (3)}{2} = \frac{3\pi}{2} \, \text{cm}.


(c) Total Perimeter:

Perimeter=AC+BC+Arc length.\text{Perimeter} = AC + BC + \text{Arc length}. Substitute the values: Perimeter=62+6+3π2.\text{Perimeter} = 6\sqrt{2} + 6 + \frac{3\pi}{2}.

So, the perimeter is: Perimeter=62+6+3π2cm.\boxed{\text{Perimeter} = 6\sqrt{2} + 6 + \frac{3\pi}{2} \, \text{cm}}.


Final Answer:

  1. Area: 18+9π4cm2\boxed{18 + \frac{9\pi}{4} \, \text{cm}^2}.
  2. Perimeter: 62+6+3π2cm\boxed{6\sqrt{2} + 6 + \frac{3\pi}{2} \, \text{cm}}.

Would you like further clarifications or examples? 😊


Related Questions:

  1. How do you calculate the area of a semicircle with a given radius?
  2. What is the formula for the hypotenuse in a right triangle?
  3. How is the arc length of a quarter circle derived?
  4. If the base and height of a triangle are doubled, what happens to its area?
  5. How does changing the radius of a circle affect the perimeter of arcs?

Tip:

Always ensure measurements of all components are clearly understood when solving composite shapes.

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Math Problem Analysis

Mathematical Concepts

Geometry
Composite Shapes
Area Calculation
Perimeter Calculation

Formulas

Area of a triangle: (1/2) * base * height
Area of a quarter circle: (1/4) * π * r^2
Arc length of a quarter circle: (1/4) * 2 * π * r
Pythagorean theorem: a^2 + b^2 = c^2

Theorems

Pythagorean Theorem

Suitable Grade Level

Grades 9-11