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A certain lighthouse is a tall thin cylinder of brick, with

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by AAPL » Mon Oct 29, 2018 4:10 am

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Answers

A

B

C

D

E

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Difficulty—

Magoosh

A certain lighthouse is a tall thin cylinder of brick, with a light chamber at the top. The brick extends from the ground to the floor of the light chamber. The brick siding of lighthouse is in need of painting. How many square feet of brick does it have?

1) The outer diameter of the brick portion of the lighthouse is 28 feet.
2) There are 274 steps from ground level to the floor of the light chamber, and each one is 8 inches high.

OA C
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by Jay@ManhattanReview » Mon Oct 29, 2018 10:55 pm
AAPL wrote:Magoosh

A certain lighthouse is a tall thin cylinder of brick, with a light chamber at the top. The brick extends from the ground to the floor of the light chamber. The brick siding of the lighthouse is in need of painting. How many square feet of brick does it have?

1) The outer diameter of the brick portion of the lighthouse is 28 feet.
2) There are 274 steps from ground level to the floor of the light chamber, and each one is 8 inches high.

OA C
Area of the brick siding of the lighthouse = πr^2h; where r = radius of the lighthouse and h = its height

Let's take each statement one by one.

1) The outer diameter of the brick portion of the lighthouse is 28 feet.

=> r = 28/2 = 14 feet. But we do not have h. Insufficient.

2) There are 274 steps from ground level to the floor of the light chamber, and each one is 8 inches high.

=> h = 274*8 = 274*8/12 feet. But we do not have r. Insufficient.

(1) and (2) together

We have both r and h, we can get the area. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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