Posted by **Anonymous** on Tuesday, February 26, 2013 at 8:35am.

A straight river flows at a speed of 20km/h. A boater starts at the south shore and heads in ths direction of 70degrees from the shore. The boat has a speed of 20km/h in still water. Find the true speed and direction of the boat.

- Maths -
**Steve**, Tuesday, February 26, 2013 at 9:46am
Let the river flow in the +x direction.

Across the river is then +y.

river velocity = (20,0)

boat velocity relative to the water

= (20cos70°,20sin70°) = (6.84,18.79)

resultant velocity relative to land

= (26.84,18.79)

speed: √(26.8^2+18.79^2) = 32.73

direction:

tanθ = y/x = 18.79/26.84 = .70

θ = 35°

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