GMAT prep boat stream problem

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 77
Joined: Tue Mar 10, 2009 3:10 am

GMAT prep boat stream problem

by subhasis8877 » Thu Jan 07, 2010 7:37 am
Please refer to the question attached
Attachments
2.jpg

User avatar
Community Manager
Posts: 1537
Joined: Mon Aug 10, 2009 6:10 pm
Thanked: 653 times
Followed by:252 members

by papgust » Thu Jan 07, 2010 10:32 pm
Time = Distance / Speed
Let upstream's time taken is 90 / v-3 + 1/2 [Since upstream journey took half an hour longer than downstream]
Let downstream's time taken is 90 / v+3

Equate the time of both upstream and downstream,

90 / v-3 + 1/2 = 90 / v+3

Solving for V, you get V as 33.

We are asked to find the total time taken for downstream journey. So, t = 90 / v + 3 = 90 / 36 = 15/6 = 2.5 hours