Monyberumen wrote:

When a cylindrical tank is filled with water at a rate of 22 cubic meters per hour, the level of water in the tank rises at a rate of 0.7 meters per hour. Which of the following best approximates the radius of the tank in meters?

A. √10/2

B. √10

C. 4

D. 5

E. 10

Let's examine what occurs in a

1-hour period

The volume of water increases by 22 cubic meters.

The height of the water increases by 0.7 meters.

So, we need to find the radius of a

0.7 meter high cylinder that has a volume of

22 cubic meters.

Volume = (pi)(radius²)(height)

22 = (pi)(radius²)(

0.7)

IMPORTANT: notice that (pi)(0.7) = approximately 2.2So, we get: 22 ≈ (2.2)(radius²)

Divide both sides by 2.2: 10 ≈ radius²

Solve: radius ≈ √10

Answer: B

Cheers,

Brent

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Brent Hanneson – GMATPrepNow.com

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