12 multiple-choice questions, progressively harder.
A rectangle has width www cm and height 999 cm. A triangle outside it is joined along the full side of width www cm and has perpendicular height 444 cm. The union area is 143143143 square centimeters. Find www.
Solution
Correct answer: A
The rectangle contributes 9w9w9w square centimeters and the triangle contributes 2w2w2w.
Compare two separate 313131 cm by 202020 cm rectangles. From each, remove a 444 cm wide and 666 cm deep rectangle. In Case A it is a corner notch; in Case B it opens into the middle of the top edge. How much larger is the perimeter in Case B?
Correct answer: C
Case A replaces equal horizontal and vertical lengths. Case B replaces the missing width by an equal notch bottom, and adds two depth edges.
Squares of side lengths 111111 cm and 999 cm have disjoint interiors and meet along exactly one segment of length 777 cm. Find their union area and perimeter.
153 cm2153\text{ cm}^2153 cm2
666666 cm
202 cm2202\text{ cm}^2202 cm2
737373 cm
808080 cm
Correct answer: B
The join has no area, so add square areas. For perimeter, remove both copies of the shared segment.
A 303030 cm by 242424 cm rectangle contains a rectangular hole of width xxx cm and height 101010 cm strictly inside. The retained area is 590590590 square centimeters. What is the total boundary length including the hole?
Correct answer: D
Recover the hole width from its missing area before finding its perimeter.
A 323232 cm by 212121 cm rectangle loses a right-triangular corner with perpendicular legs 999 cm and 121212 cm along the rectangle sides. Find the retained area and perimeter.
564 cm2564\text{ cm}^2564 cm2
100100100 cm
618 cm2618\text{ cm}^2618 cm2
106106106 cm
121121121 cm
The removed area is half the product of its legs. Pythagoras gives a 151515 cm new diagonal edge, replacing the two removed legs.
Two polygonal regions have areas 132132132 and 909090 square centimeters. Their union has area 190190190 square centimeters. What is the area common to both?
The sum of the separate areas exceeds the union by exactly the common area.
Two disjoint polygonal regions have areas 350350350 square millimeters and 0.0180.0180.018 square meters. Use 111 cm equal to 101010 mm and 111 m equal to 100100100 cm. What is their combined area in square centimeters?
Each square centimeter contains 100100100 square millimeters, and each square meter contains 100001000010000 square centimeters.
A 282828 cm by 191919 cm rectangle has a rectangular notch 121212 cm wide and 888 cm deep opening into the middle of the top edge. What is the remaining polygon's perimeter?
The removed top width is replaced by an equal notch bottom. The two new depth edges add 161616 cm.
A trapezoid has parallel bases 262626 cm and 141414 cm and perpendicular height 151515 cm. A rectangular strip of height 151515 cm lies entirely within the trapezoid and spans between its parallel bases. Removing the strip leaves 225225225 square centimeters. What is the strip width?
The full trapezoid area is 300300300 square centimeters. The strip occupies the missing 757575 square centimeters.
A 191919 cm by 111111 cm rectangle contains a rectangular hole strictly inside. The hole is 404040 mm high, and the retained area is 193193193 square centimeters. Use 101010 mm equal to 111 cm and 100100100 cm equal to 111 m. What is the total boundary length, including the hole, in meters?
Convert the hole height to 444 cm. Its area is 209−193209-193209−193, or 161616 square centimeters, so its width is 444 cm.
A 333333 cm by 171717 cm rectangle contains two holes strictly inside it with disjoint interiors. One is a right triangle with perpendicular legs 888 cm and 999 cm. The other is a 777 cm by 444 cm rectangle. What area remains?
The holes have no common area, so subtract each once from the outside rectangle.
A simple polygon is decomposed in two different ways. Each decomposition uses pieces with disjoint interiors and covers exactly the polygon. What must be true?
Area addition applies separately to both decompositions. Both sums measure the same whole.
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