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 Two Boats and A River (Posted on 2003-11-13)
Two boats on opposite sides of a river head towards each other at different speeds. When they pass each other the first time they are 700 yards from one shoreline. They continue to the opposite shoreline, turn around, and move towards each other again. When they pass the second time they are 300 yards from the other shoreline.

How wide is the river? (Assume both boats travel at a constant speed and ignore factors such as turn-around time and the current of the river).

 Submitted by Ravi Raja Rating: 2.5000 (4 votes) Solution: (Hide) Define the following variables: w=width of river s1=speed of first boat s2=speed of second boat t1=time until boats meet the first time t2=time until boats meet the second time I shall arbitrarily say that both boats are 700 yards from the shore of original of the first boat at time t1. The following equations can be inferred from the information given: (1) w=t1*(s1+s2) (2) s1*t1=700 (3) w+300=s1*t2 (4) 2w-300=s2*t2 Adding equations (1) and (2) we get: (5) 3w=t2*(s1+s2) Substituting s1+s2=w/t1 from equation (1) we get: 3w=t2*r/t1 3w*t1=r*t2 (6) 3*t1=t2 Combining equations (3) and (6): (7) w+300=3*s1*t1 Combining equations (2) and (7): w+300=2100 w=1800

 Subject Author Date Solution Dej Mar 2008-07-16 00:59:06 Answer K Sengupta 2008-03-20 09:44:57 trial and error rixar 2004-07-23 21:03:33 Solution Senthil Kumar 2003-11-14 13:39:23 re(2): Can someone please tell me where I went wrong ? Dan 2003-11-13 21:42:19 re: Can someone please tell me where I went wrong ? SilverKnight 2003-11-13 21:11:38 Can someone please tell me where I went wrong ? Dan 2003-11-13 20:53:05 re: In Defense of Limited Equations SilverKnight 2003-11-13 20:12:08 Current Events Dan 2003-11-13 20:07:08 In Defense of Limited Equations Gordon Steel 2003-11-13 19:50:07 re: Solution Without Almost No Equations SilverKnight 2003-11-13 16:05:53 Solution Without Almost No Equations Gordon Steel 2003-11-13 15:16:49 solution Charlie 2003-11-13 14:53:18 Full Solution SilverKnight 2003-11-13 14:43:06

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