Bunuel wrote:
Little Texas Drilling Company has three wells, each producing oil at a constant rate. Well A produces one barrel every two minutes. Well B produces one barrel every three minutes. Well C produces one barrel every four minutes. How many hours does it take Little Texas Drilling Company to produce 165 barrels of oil?
(A) 2
(B) 3
(C) 4
(D) 18
(E) 180
We are given that well A produces one barrel every two minutes, well B produces one barrel every three minutes, and well C produces one barrel every four minutes. Since rate = work/time, well A’s rate = 1/2, well B’s rate = 1/3, and well C’s rate = 1/4.
If we let t = the time in minutes during which the wells work together, we can create the following equation to determine t:
(1/2)t + (1/3)t + (1/4)t = 165
Multiplying the entire equation by 12, we have:
6t + 4t + 3t = 1980
13t = 1980
t = 1980/13 = 152.3 minutes
Since 152.3 minutes = 2.54 hours, the correct answer choice is B.
Alternative solution:
Since well A produces one barrel every two minutes, it can produce 30 barrels in an hour. Likewise, since well B produces one barrel every three minutes and well C produces one barrel every four minutes, they can produce 20 and 15 barrels an hour, respectively. Thus, in one hour, these 3 wells can produce 30 + 20 + 15 = 65 barrels. Thus, it takes them 165/65 = 2.54 hours to produce 165 barrels.
[Note: Something is wrong with this problem, because the exact time is 2.54 hours, which can be rounded to 3, but I think they really want the answer to be exactly 3. If that is the case, the total number of barrels should be 195 barrels, not 165 barrels.]
Answer: B
_________________
See why Target Test Prep is the top rated GMAT course on GMAT Club.
Read Our Reviews