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May 3rd, 2017, 01:28 PM  #1 
Senior Member Joined: Jan 2017 From: US Posts: 104 Thanks: 5  Solve For the Speed Of The Current A fish can swim 45 miles downriver in the same amount of time that it can swim 27 miles upriver. Solve for the speed of the current if the speed of the fish is 12 mph in still water. Show all of your work and explain your solution. 
May 3rd, 2017, 01:44 PM  #2 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,780 Thanks: 1025 Math Focus: Elementary mathematics and beyond 
Where are you having difficulty?

May 3rd, 2017, 01:48 PM  #3  
Senior Member Joined: Sep 2015 From: USA Posts: 1,849 Thanks: 957  Quote:
clearly the current is in the direction of down river $v_{up} = v_{still}v_{current}$ $v_{down} = v_{still}+v_{current}$ $v = \dfrac d t$ $t=\dfrac d v$ $\dfrac{45}{ v_{still}+v_{current}}=\dfrac{27}{ v_{still}v_{current}}$ see if you can finish  
May 3rd, 2017, 01:51 PM  #4 
Senior Member Joined: Jan 2017 From: US Posts: 104 Thanks: 5 
Thanks! I was having difficulty constructing the equation, but I think romsek answered my question.

May 3rd, 2017, 02:22 PM  #5  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,780 Thanks: 1025 Math Focus: Elementary mathematics and beyond  Quote:
Why did you ignore my post, other than clicking "Thanks"?  
May 3rd, 2017, 03:41 PM  #6 
Senior Member Joined: Sep 2015 From: USA Posts: 1,849 Thanks: 957  
May 3rd, 2017, 04:13 PM  #7 
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,780 Thanks: 1025 Math Focus: Elementary mathematics and beyond 
You could have edited your post.

May 3rd, 2017, 06:12 PM  #8 
Senior Member Joined: Jan 2017 From: US Posts: 104 Thanks: 5 
I'm just saying... I posted this question hoping for helpful steps to get to the solution. I don't see why there is a problem with what Romsek posted, and it's not because I'm trying to cheat. He didn't even give the answer, if demonstrated how to set up the formulas. If you're a moderator and feel there is sincerely a problem with what he posted, fine. But I don't see what the problem is.
Last edited by Indigo28; May 3rd, 2017 at 06:24 PM. 
May 3rd, 2017, 06:49 PM  #9 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,088 Thanks: 795 
c = current speed @(12+c)..............45..................>h hours @(12c)........27........>h hours 45 / (12+c) = 27 / (12c) 

Tags 
algebra, current, inverse variation, solve, speed 
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