Math Problem Statement
Solution
The composite shape in the image consists of two distinct parts:
-
A trapezoid with the following dimensions:
- Bottom base: 20 inches
- Top base: 8 inches
- Height: 8 inches
- The slant height of each side of the trapezoid is 10 inches.
-
A semicircle placed on top of the trapezoid:
- The diameter of the semicircle is 8 inches (since it matches the top base of the trapezoid).
- Therefore, the radius of the semicircle is inches.
Step 1: Perimeter Calculation
The perimeter consists of:
- The perimeter of the trapezoid (two slanted sides and the bottom base).
- The perimeter of the semicircle (its curved part).
1.1 Trapezoid's perimeter:
- Bottom base = 20 inches
- The two slanted sides = 10 inches each
The straight top edge is covered by the diameter of the semicircle, so we exclude it from the perimeter. The perimeter contribution from the trapezoid is:
1.2 Semicircle's perimeter:
The curved part of the semicircle’s perimeter is half of the circumference of a full circle:
Thus, the total perimeter of the shape is:
Step 2: Area Calculation
The total area consists of the area of the trapezoid and the area of the semicircle.
2.1 Trapezoid's area:
The area of a trapezoid is given by the formula: Where:
- inches (bottom base)
- inches (top base)
- inches (height)
Substituting these values:
2.2 Semicircle's area:
The area of a semicircle is half the area of a full circle:
2.3 Total area:
The total area is the sum of the areas of the trapezoid and the semicircle:
Final Results:
- Perimeter: 52.56 inches
- Total area: 137.12 square inches
Would you like further details or have any questions? Here are 5 related questions to expand your understanding:
- How would the perimeter change if the radius of the semicircle doubled?
- What is the formula for the perimeter of a full circle and how would it be applied here?
- How do you calculate the area of a trapezoid if the bases are not parallel?
- If the trapezoid had different slant heights, how would that affect the perimeter calculation?
- What if the shape were a full circle instead of a semicircle—how would the area change?
Tip: When working with composite shapes, always calculate areas and perimeters for individual parts before combining them for accurate results.
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Math Problem Analysis
Mathematical Concepts
Geometry
Perimeter Calculation
Area Calculation
Composite Shapes
Formulas
Perimeter of a trapezoid: P_trapezoid = a + b + c (excluding the top base covered by the semicircle)
Perimeter of a semicircle: C_semicircle = π * r
Area of a trapezoid: A_trapezoid = 1/2 * (b1 + b2) * height
Area of a semicircle: A_semicircle = 1/2 * π * r^2
Theorems
Formula for circumference and area of a circle
Area of a trapezoid
Suitable Grade Level
Grades 8-10
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