Question

A kayaker needs to paddle north across a 85 m wide harbor. The tide is going out, creating a tidal current that flows to the east at 1.6 m/s. The kayaker can paddle with a speed of 2.8 m/s.

(a) In which direction should he paddle in order to travel straight across the harbor?

Answer 1

85/2.8=30.36 secs. to travel straight across. in the time he would have end up (30.36 x 1.6) = 48.57 m. downstream so now you can sketch a right triangle, 85 m. north/south, south 48.57 m. "upstream" on the far bank.
(a) angle to row = 48.57/85 = 0.57 deg, west of north.
(b) distance he actually paddles = sqrt. (85^2 + 48.57^2), 98 meters
time 98/2.8 = 35 secs