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 Author: Gennadiy [ Thu Jan 24, 2013 3:55 pm ] Post subject: GMAT Rate Joe is painting a rectangular room whose dimensions are given by a, b and c meters. Joe takes 8 hours to paint a wall with dimensions a and c. He takes 4 hours to paint a wall with dimensions b and c and 12 hours to paint the ceiling with dimensions a and b. If Joe works at a constant rate and a = 6, then what is the volume of the room?A. 18 cubic metersB. 24 cubic metersC. 30 cubic meters D. 36 cubic metersE. It can’t be determined.(D) This is a typical work problem with an addition, finding the volume. Start by finding the area of the two walls and the ceiling.Wall 1 has the area ac, and it took 8 hours to paint it. So the area Joe paints in one hour is (ac)/8.Wall 2 has area bc, and took 4 hours to paint. So the area Joe paints in one hour is (bc)/4.The ceiling has the area ab, and it took 12 hours to paint it. So the area Joe paints in one hour is (ab)/12.Since Joe is working at a constant rate, the area painted in one hour is the same. So (bc)/4 = (ab)/12 .Since a = 6, (bc)/4 = (6b)/12 .So c = 4 × 6 / 12 .c = 2(ac)/8 = (bc)/4, where a = 6 and c = 2. So (6 × 2)/8 = (b × 2)/4.b = 3This gives a = 6 meters, b = 3 meters, and c = 2 meters. The volume of the room is a × b × c = 6 × 3 × 2 = 36 cubic meters.So the correct answer is choice (D).

 Author: clover [ Thu Jan 24, 2013 4:01 pm ] Post subject: Re: GMAT Rate woah good prob. threw me off when i read it for the first time...

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