# speed question

• September 22nd 2008, 03:42 PM
andrewpark2
speed question
It took a crew 80 min to row 3 km upstream and back again. If the rate of flow of the stream was 3km/h, what was the rowing rate of the crew?
• September 22nd 2008, 04:10 PM
masters
Quote:

Originally Posted by andrewpark2
It took a crew 80 min to row 3 km upstream and back again. If the rate of flow of the stream was 3km/h, what was the rowing rate of the crew?

Total distance is 3 km (1.5 km each way)
Total time is 4/3 hr (80 min)
Rate of steam is 3 km/hr

rate of boat downstream = b + 3
rate of boat upstream = b - 3

$d = rt$

$t=\frac{d}{r}$

$\frac{1.5}{b+3} + \frac{1.5}{b-3}=\frac{4}{3}$

Does that sound reasonable?