Posted by **Taina** on Friday, June 24, 2011 at 12:18pm.

Rowing. Abby rows 10 km upstream and 10 km back in a total time of 3 hr. The speed of the river is 5km/h. Find Abby’s speed in still water.use five-step problem solving process

- math -
**Reiny**, Friday, June 24, 2011 at 1:21pm
Don't know what the "five-step process" is, but here is how I would solve it ....

let her speed in still water be x km/h

time to go upstream = 10/(x-5)

time to go downstream = 10/(x+5)

solving : 10/(x-5) + 10/(x+5) = 3

10x + 50 + 10x - 50 = 3x^2 - 75

3x^2 - 20x - 75 = 0

x = (20 ± √1300)/6

= 9.34 km/h or a negative, which we reject

her still-water speed is 9.34 km/h

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