Geometry Practice Test: Area and Perimeter of Plane Figures
- Area and Perimeter
- 10 questions
- 14 minutes
Questions mix formulas with composite figures and scale changes. Tip: in composite shapes, check which edges are really on the outside before adding a perimeter.
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Question 1
A parallelogram has a base of 12 cm, a slanted side of 8 cm and a height of 6 cm.
What is its area?
Correct answer: D
Area of a parallelogram is base × height: 12 · 6 = 72 cm². Multiplying by the slanted side, 12 · 8 = 96, uses a length that is not perpendicular to the base.
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Question 2
A circle has a circumference of 18π inches.
What is its area?
Correct answer: B
From 2πr = 18π, r = 9, so the area is π · 9² = 81π in². Using 18 as the radius gives 324π.
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Question 3
The diagonals of a rhombus are 14 m and 9 m long.
What is the area of the rhombus?
Correct answer: A
The area of a rhombus is half the product of its diagonals: (14 · 9)/2 = 63 m². The value 126 m² forgets to halve.
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Question 4
A rectangle has a perimeter of 46 ft and a length of 15 ft.
What is its area?
Correct answer: C
Two widths are 46 − 2 · 15 = 16 ft, so the width is 8 ft and the area is 15 · 8 = 120 ft². Using 31 as the width (46 − 15) gives 465 ft².
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Question 5
What is the area of an equilateral triangle with sides of 8 cm?
Correct answer: B
The height is 43 cm (a 30-60-90 triangle), so the area is ½ · 8 · 43 = 163 cm². The formula (3/4)s² gives the same result.
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Question 6
Each side of a square is tripled. By what factor is the area multiplied?
Correct answer: D
Area scales by the square of the scale factor: 3² = 9. The factor 27 is the change for volume, not area.
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Question 7
A 4 m by 4 m square is cut out of one corner of a 20 m by 12 m rectangle.
What is the perimeter of the remaining shape?
Correct answer: B
Cutting a corner removes 4 m from two sides but adds two new inside edges of 4 m each, so the perimeter stays 2(20 + 12) = 64 m. Subtracting 8 m gives 56 m, which forgets the new edges.
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Question 8
A running field is a 100 m by 60 m rectangle with a semicircle attached to each 60 m end.
To the nearest tenth of a meter, what is the distance once around the outside of the field?
Correct answer: C
The outside is two 100 m straight sides plus two semicircles of diameter 60 m, which together make one full circle: 200 + 60π ≈ 388.5 m. The value 294.2 m uses only one semicircle.
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Question 9
A square is inscribed in a circle with radius 5 cm, so its corners lie on the circle.
To the nearest tenth, what is the area of the region inside the circle but outside the square?
Correct answer: A
The square's diagonal is the diameter, 10 cm, so its area is 10²/2 = 50 cm². The circle's area is 25π ≈ 78.5 cm², and 78.5 − 50 ≈ 28.5 cm².
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Question 10
A triangle has sides of 13, 14 and 15 units. The altitude to the side of length 14 is 12 units long.
What is the area of the triangle?
Correct answer: D
Area = ½ · base · height = ½ · 14 · 12 = 84 square units. Forgetting the ½ gives 168; the side 13 or 15 is not the height for base 14.
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