12 multiple-choice questions, progressively harder.
A ball has volume 288π cm3288\pi\text{ cm}^3288π cm3. What is its radius?
Solution
Correct answer: B
Cancel pi and isolate the radius cubed.
A sphere has area 324π cm2324\pi\text{ cm}^2324π cm2. What is its diameter?
Correct answer: D
Use surface area to find the positive radius, then double it.
A hemisphere has radius 2.5 cm. What is its exact volume?
Correct answer: A
Cube the radius before multiplying by two-thirds pi.
A solid hemisphere has total boundary area 243π cm2243\pi\text{ cm}^2243π cm2, including its flat base. What is its radius?
Correct answer: C
The total includes the curved cap and one base disk.
The disk bounded by a sphere's great circle has area 36π cm236\pi\text{ cm}^236π cm2. What is the sphere's area?
The great-circle disk and sphere share a radius. The sphere area is four times the disk area.
A ball has radius 10 cm. A plane lies 8 cm from its center, measured perpendicularly. What is the area of the filled section?
Pythagoras gives the section radius squared directly.
In the hemisphere comparison, the cylinder radius and height are 6 cm. The removed cone apex is at the bottom center and its top radius is 6 cm. What section area remains at height 2 cm above the bottom?
Similar triangles give cone radius 2 cm at that level. Subtract its section from the cylinder disk.
A comparison cylinder and removed cone each have positive radius R and height R. The cone apex is at the bottom, where height z is zero. Which formula gives the cone section radius for every height z from zero to R?
The radius and the distance up from the apex grow in the same ratio. Since top radius and height are both R, their ratio is one. This gives the section radius at every height, including the bottom apex.
A ball is cut through its center into two solid hemispheres. How does the volume of either piece compare with the original volume?
The cut divides the ball into two congruent regions with nonoverlapping interiors. Each has half the original volume. The new flat boundary changes area, not the amount of either half.
The largest plane section of a ball has disk area 49π cm249\pi\text{ cm}^249π cm2. What is the ball volume?
The largest section is central, with the ball radius. Its area gives radius 7 cm.
A ball has volume 36π cm336\pi\text{ cm}^336π cm3. What is the circumference of a great circle?
Recover the positive radius from volume, then use that same radius for the great circle.
An ideal spherical surface has radius 0.8 m. What is its exact area?
Square 0.8 before multiplying by four pi.
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