Retired Moderator
Joined: 07 Jun 2014
Posts: 4810
Given Kudos: 0
WE:Business Development (Energy and Utilities)
Re: One robot, working independently at a constant rate, can ass
[#permalink]
10 Jul 2018, 06:16
Explanation
Note that choice (D) is a trap. This issue is relatively rare, but it’s worthwhile to be able to recognize it if you see it. In this case, each robot is independently assembling complete doghouses.
Since the question asks for the number of completed doghouses after \(2\frac{1}{2}\) hours, any incomplete doghouses must be removed from the calculations.
Since one robot completes a doghouse in 12 minutes, the individual hourly rate is 60 ÷ 12 = 5 doghouses per hour.
Therefore, each robot produces 5 × 2.5 = 12.5 doghouses in \(2\frac{1}{2}\) hours. (Or just divide the 150 total minutes by 12 minutes per doghouse to get the same result.)
However, the questions asks about completed doghouses, and the robots are working independently, so drop the decimal. Each robot completes only 12 complete doghouses in the time period, for a totalof 12 × 10 = 120 doghouses.