Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

Printable View

- Nov 25th 2008, 10:18 PMmagentaritaBoat in Still Water
Debbie traveled by boat 5 miles upstream to fish in her favorite spot. Because of the 4-mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

- Nov 26th 2008, 08:13 AMgreat_math
Let the speed in still water be $\displaystyle x$ mph

When it travels upstream its speed= $\displaystyle x-4$ mph

Time taken to go upstream= $\displaystyle \frac{5}{x-4}$ h

Speed in downstream = $\displaystyle x+4$ mph

Time taken to go downstream or time taken to return back= $\displaystyle \frac{5}{x+4}$ h

And 20 min $\displaystyle = \frac{20}{60}=\frac{1}{3}$ hrs

But according to question...

$\displaystyle \frac{5}{x-4} -\frac{5}{x+4}=\frac{1}{3}$

Solve it and you will get the answer - Nov 28th 2008, 05:00 AMmagentaritawow.....
- Nov 28th 2008, 05:06 AMgreat_math
- Nov 28th 2008, 09:08 AMmagentaritaok..........