MathRevolution wrote:

[GMAT math practice question]

Water enters a cylindrical barrel at a constant speed of \(500 cm^3/min\), and the height of the barrel increases at a constant speed of \(10\) cm per minute. What is the approximate radius of the barrel, in centimeters?

A. 1

B. 2

C. 3

D. 4

E. 5

Formula used: Volume = \(\pi * r^2 * h\) where \(r\) - radius of the cylinder & \(h\) - height of the cylinder

Water in the cylindrical barrel rises 10 cm in a minute, when \(500 cm^3\) of water enters the cylinder in a minute

This also means that the height of the barrel is 10 cm when a volume of \(500 cm^3\) water enters the barrel.

Substituting values \(500 = \pi * r^2 * 10\) -> \(500 = r^2 * 31.4\) (\(\pi = 3.14\)) -> \(r^2 = \frac{500}{31.4} = 16\)(approximately)

Therefore, the approximate radius of the cylinder barrel is \(\sqrt{16} = 4\)

(Option D)
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