SOLUTION: The current in a river is 4 kph. Al can row from home to his fishing spot 5 km down river and back home again in 3 hours. What is Al's rowing rate in still water?

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Question 843111: The current in a river is 4 kph. Al can row from home to his fishing spot 5 km down river and back home again in 3 hours. What is Al's rowing rate in still water?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

What is Al's rowing rate highlight_green%28x%29in still water?

t = D/r

*** 5km%2F%28x%2B4kph%29+%2B+5km%2F%28x-4kph%29+=+3hr+|Multiplying thru by (x+40(x-4) so as all denominators = 1

  5(x-4) + 5(x+4) = 3(x+4)(x-4)

      10x = 3x^2 - 48

     3x^2 - 10x - 48 = 0

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+

x+=+%2810+%2B-+sqrt%28+676+%29%29%2F%286%29+

x+=+%2810+%2B-+26%29%2F%286%29+

   x = 6,   (tossing out negative solution for unit measure)

  6kph is Al's rowing rate in still water

CHECKING our answer***

 5/10 + 5/2  = 5/10 + 25/10 = 30/10 = 3hr

Wish You the Best in your Studies.