SOLUTION: A river is flowing downstream at a rate of 2 metres per second. Brendan, who has an average swimming speed of 3 metres per second, decides to go for a swim in the river. He dives i

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Question 952059: A river is flowing downstream at a rate of 2 metres per second. Brendan, who has an average swimming speed of 3 metres per second, decides to go for a swim in the river. He dives into the river and swims downstream to a certain point then swims back upstream to the starting point. The total time taken is 4 minutes. How far did Brendan swim downstream?

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Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The current, +c+=+2+ m/sec
Swimming speed is +s+=+3+ m/sec
+3+%2B+2+=+5+ m/sec downstream
+3+-+2+=+1+ m/sec upstream
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Let +d+ = one-way distance he swims
Let +t+ = his time in minutes to go downstream
Convert +4+ min to sec
+4%2A60+=+240+ sec
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Equation for downstream:
(1) +d+=+5%2At+
Equation for upstream:
(2) +d+=+1%2A%28+240+-+t+%29+
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Substitute (1) into (2)
(2) +5t+=+240+-+t+
(2) +6t+=+240+
(2) +t+=+40+
and
(1) +d+=+5%2At+
(1) +d+=+5%2A40+
(1) +d+=+200+
He swam 200 m
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check:
(2) +d+=+1%2A%28+240+-+t+%29+
(2) +200+=+1%2A%28+240+-+40+%29+
(2) +200+=+200+
OK