SOLUTION: A boat traveled 210 miles downstream and back. The trip downstream took 10 hours. The trip back took 70 hours. What is the speed of the boat in still water? What is the speed of t

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Question 133442: A boat traveled 210 miles downstream and back. The trip downstream took 10 hours. The trip back
took 70 hours. What is the speed of the boat in still water? What is the speed of the current?
Answer by josmiceli(6785) About Me  (Show Source):
You can put this solution on YOUR website!
Let c= speed of the current
Let b= speed of the boat
I'm not sure what "210 mi downstream and back" means
I'm assuming it means 105 mi one way and 105 back
(distance traveled against current) = (distance travelled with current)
d+=+210%2F2
d+=+105mi
For downstream:
105%2F10+=+10.5 mi/hr
For upstream:
105%2F70+=+1.5mi/hr
b+%2B+c+=+10.5
b+-+c+=+1.5
Add these
2b+=+12
b+=+6mi/hr
b+-+c+=+1.5
6+-+c+=+1.5
c+=+4.5mi/hr
The speed of the boat in still water is 6 mi/hr
The speed of the current is 4.5 mi/hr
check answers:
%28b+%2B+c%29%2A10+=+%28b+-+c%29%2A70
%286+%2B+4.5%29%2A10+=+%286+-+4.5%29%2A70
105+=+105
OK