Gmat_mission wrote: ↑Thu Nov 19, 2020 11:34 am
What is the volume of the right circular cylinder \(X?\)
(1) The height of \(X\) is \(20.\)
(2) The base of \(X\) has area \(25\pi.\)
Answer:
C
Source: Official Guide
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 [m]= \pi r^2 h[/m]
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 [m]= \pi r^2[/m]
So statement 2 is telling us that: [m] \pi r^2 = 25 \pi[/m]
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 [m]h = 20[/m]
Statement 2 tells us that [m] \pi r^2 = 25 \pi[/m]
So
the volume of the cylinder [m]= \pi r^2 h = (25 \pi)(20) = 500 \pi[/m]
Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer: C
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
