BTGmoderatorLU wrote: ↑

Wed Jul 07, 2021 4:39 pm

Source: Official Guide

What is the volume of the right circular cylinder X?

1) The height of X is 20.
2) The base of X has area \(25\pi.\)

The OA is C

Target question: What is the volume of the right circular cylinder X ?
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Aside: A right circular cylinder is a cylinder whose bases are aligned directly above the other.
So, the cylinder on the left (below) is a right cylinder, and the one on the right is an oblique cylinder

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Key property: Area of cylinder = pi r^2 h

Statement 1: The height of X is 20
Since we still don't know the radius of the cylinder, statement 1 is NOT SUFFICIENT

Statement 2: The base of X has area 25π.
Area of a circle = pi r^2
So statement 2 is telling us that: pi r^2 = 25 pi
Since we still don't know the height of the cylinder, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that h = 20
Statement 2 tells us that pi r^2 = 25 pi
So the volume of the cylinder = pi r^2 h = (25 pi)(20) = 500 pi
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,
Brent