12 multiple-choice questions, progressively harder.
A square and a regular hexagon each have perimeter 24 cm. Which has greater area, and by how much?
Solution
Correct answer: D
The square side is 6 cm, giving area 36 square cm. The hexagon side is 4 cm, giving exact area 24 times the square root of 3 square cm.
The hexagon has the greater area, and subtracting 36 gives the stated difference.
Which complete list of exact dimensions can belong to a square? All lengths use centimeters.
Correct answer: B
A square has apothem half its side, and its 45-45-90 half-triangle has radius the apothem times the square root of 2. Only the list with apothem 5 and radius 5 times the square root of 2 meets both conditions.
A regular octagon has radius 12 cm. What is its area to the nearest tenth of a square centimeter? Use degrees.
Correct answer: A
Use half-central angle 22.5 degrees. Keep calculator precision for the apothem and side.
The half-central angle of a convex regular polygon is 7.5 degrees. How many sides does the polygon have?
Correct answer: C
The half-central angle is 180 degrees divided by the side count.
A square and a regular hexagon both have apothem 2 cm. What is the hexagon-to-square area ratio?
The square side is 4 cm, so its area is 16 square cm. For the hexagon, the side is 4 divided by the square root of 3 cm.
Dividing by 16 gives the ratio square root of 3 to 2.
For a regular pentagon with positive side length x, which expression gives its area? Use degrees.
The perimeter is 5x and the apothem is x divided by twice the tangent of 36 degrees. Substitute both into the area formula.
A convex regular polygon has side length exactly twice its apothem. How many sides does it have?
Half a side equals the apothem, so the right half-triangle has equal legs. Its half-central angle is 45 degrees.
An equilateral triangle has radius 18 cm. What is its exact area?
The 60-degree half-triangle has apothem 9 cm and half-side 9 times the square root of 3 cm. The full perimeter is 54 times the square root of 3 cm.
A regular hexagon has apothem 15 cm. Which is its radius?
In its 30-60-90 right half-triangle, the apothem is the longer leg. Divide by the square root of 3 for the shorter leg, then double for the hypotenuse.
Can a convex regular polygon have a half-central angle of exactly 27 degrees?
The side count would have to satisfy
A polygon needs an integer number of sides. Rounding this number would change the exact angle.
A regular decagon has apothem 7 cm. What is its area to the nearest tenth? Use degrees.
The half-central angle is 18 degrees. The half-side is 7 times the tangent of 18 degrees.
A convex regular polygon has central angle 20 degrees and apothem 4 cm. Which expression gives its area in square centimeters? Use degrees.
There are 18 sides, and the right half-triangle uses angle 10 degrees.
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