12 multiple-choice questions, progressively harder.
A closed regular square pyramid has total area 384 cm2384\text{ cm}^2384 cm2 and base side 121212 cm. Find its perpendicular height.
Solution
Correct answer: D
The base area is 144144144 square centimeters, leaving lateral area 240240240. The perimeter is 484848 cm.
A right cone has curved area 84π cm284\pi\text{ cm}^284π cm2 and slant height 141414 cm. What sector angle forms its curved side?
Correct answer: B
Reverse the curved-area formula to get radius 666 cm. Then use the radius ratio.
A sector of radius 202020 cm and angle 216∘216^\circ216∘ forms a right cone without overlap. Find the cone's closed surface area.
Correct answer: C
The sector arc is 3/53/53/5 of a radius-202020 circumference, giving base radius 121212 cm. Its slant height is 202020 cm.
Two right cones have base radius 333 cm. Their perpendicular heights are 444 cm and 55\sqrt{55}55 cm. How much greater is the second cone's lateral area?
Correct answer: A
The first slant height is 555 cm and the second is 888 cm, by adding the squared radius to each height-square.
Lateral area changes with slant height, not directly with perpendicular height.
A regular square pyramid has slant height 151515 cm and apex-to-base-vertex edges 171717 cm. Find its closed total surface area.
Within one isosceles side face, half the base edge is a leg and 171717 cm is the hypotenuse.
The perimeter is 646464 cm and the square area is 256256256 square centimeters.
A regular hexagonal pyramid has base side 666 cm and perpendicular height 73\sqrt{73}73 cm. Find its lateral area.
The regular hexagon's apothem is 333\sqrt333 cm, so its square is 272727.
A sector has radius 888 cm and angle 270∘270^\circ270∘. It is rolled into a right cone without overlap. Which pair gives the base radius and perpendicular height?
r=8 cmr=8\text{ cm}r=8 cm
h=6 cmh=6\text{ cm}h=6 cm
r=6 cmr=6\text{ cm}r=6 cm
h=27 cmh=2\sqrt7\text{ cm}h=27 cm
r=3 cmr=3\text{ cm}r=3 cm
h=55 cmh=\sqrt{55}\text{ cm}h=55 cm
h=73 cmh=\sqrt{73}\text{ cm}h=73 cm
The sector uses three quarters of a full circumference. Thus the cone radius is three quarters of 888, or 666 cm.
A closed right cone has total area 180π cm2180\pi\text{ cm}^2180π cm2 and radius 666 cm. Find its perpendicular height.
The base disk has area 36π36\pi36π square centimeters, leaving curved area 144π144\pi144π.
A regular square pyramid has base side 141414 cm and slant height 252525 cm. Find the volume using the actual perpendicular height.
The base apothem is 777 cm, so the perpendicular height is 242424 cm.
The given slant height measures a face, not the volume height.
A pyramid with square base side 101010 cm has two side-face altitudes of 61\sqrt{61}61 cm and two of 41\sqrt{41}41 cm. Find its lateral area from those face data.
Two faces have each altitude. Find the two pair areas separately.
Add and factor the common coefficient.
The unequal altitudes cannot be replaced by one common slant height.
A right cone has base radius 777 cm. Its closed total surface area is three times its lateral area. Can a nondegenerate right cone satisfy this condition?
The proposed relation would make the base area twice the lateral area.
But positive perpendicular height requires slant height greater than radius, so the proposed measurements are incompatible.
A right-conical shell has base circumference 18π18\pi18π cm and curved-side area 117π cm2117\pi\text{ cm}^2117π cm2. It has no base disk. Find the sector radius and sector angle for its pattern.
9 cm9\text{ cm}9 cm
360∘360^\circ360∘
13 cm13\text{ cm}13 cm
324013∘\frac{3240}{13}^\circ133240∘
162013∘\frac{1620}{13}^\circ131620∘
26 cm26\text{ cm}26 cm
The circumference gives base radius 999 cm. The curved area then gives slant height 131313 cm, which becomes the sector radius.
The slant height exceeds the radius, so a positive perpendicular height exists.
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