SOLUTION: it took a boat 2 hours to reach town A going upstream. The way back 1 hour and 20 minutes. What is the speed of the boat in still water if the speed of the stream is 3 MPH

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Question 1051683: it took a boat 2 hours to reach town A going upstream. The way back 1 hour and 20 minutes. What is the speed of the boat in still water if the speed of the stream is 3 MPH
Found 2 solutions by josmiceli, stanbon:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = the speed of the boast in still water
Let +d+ = the one-way distance traveled
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Equation for going upstream:
(1) +d+=+%28+s+-+3+%29%2A2+
Equation for going downstream:
(2) +d+=+%28+s+%2B+3+%29%2A%284%2F3%29+
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By substitution:
(2) +%28+s+-+3+%29%2A2+=+%28+s+%2B+3+%29%2A%28+4%2F3%29+
(2) +2s+-+6+=+%284%2F3%29%2As+%2B+4+
(2) +%282%2F3%29%2As++=+10+
(2) +s+=+%283%2F2%29%2A10+
(2) +s+=+15+
The speed of the boat in still water is 15 mi/hr
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check answer:
(1) +d+=+%28+15+-+3+%29%2A2+
(1) +d+=+12%2A2+
(1) +d+=+24+
and
(2) +d+=+%28+15+%2B+3+%29%2A%284%2F3%29+
(2) +d+=+18%2A%284%2F3%29+
(2) +d+=+24+
OK

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
It took a boat 2 hours to reach town A going upstream. The way back 1 hour and 20 minutes. What is the speed of the boat in still water if the speed of the stream is 3 MPH
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Upstream DATA:
time = 2 hrs ; rate = b-3 mph ; dist = 2(b-3) = 2b-6 miles
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Downstream DATA:
time = (4/3) hrs ; rate = b+3 mph ; dist = (4/3)(b+3) = (4/3)b + 4 miles
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Equation:
dist up = dist down
2b-6 = (4/3)b + 4
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(2/3)b = 10
b = 15 mph (speed of the boat in still water)
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Cheers,
Stan H.
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