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

This topic has expert replies
Moderator
Posts: 2237
Joined: Sun Oct 29, 2017 2:08 pm
Followed by:2 members

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

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

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members

by Jay@ManhattanReview » Mon Oct 29, 2018 10:55 pm

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

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
_________________
Manhattan Review GMAT Prep

Locations: Manhattan Review India | Hyderabad GMAT Prep | Bangalore GMAT Courses | Kukatpally GMAT Prep | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.