- AleksandrM
- Legendary Member
- Posts: 566
- Joined: Fri Jan 04, 2008 11:01 am
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- GMAT Score:640
its a trick question.
the answer is 4 hours.
it asks for the LEAST amount of time B must operate.
Therefore we need to find how much A can produce by itself in 8 hours.
= 9k * 8 =72k
100k is our goal, so b needs to produce 100k-72k = 28k
b produces 7k per hour => 28k/7k = 4 hours.
p.s.
What did you get on this practice test? (I remember I also had this as the last question in my GMATprep test 2 and I ended with a 48 raw on that test I believe)













