Question

A boat is at a point 120km West and 60km South of its destination. It sails in water which has a current of 20km/h North. In order to arrive at the destination, the captain decides to head the boat due East at 50km/h until he reaches a point due South of the destination. He would then let the boat drift towards the destination. For what length of time should each portion of the trip last?

I got 2.4h for the captain heading east. I need to know how long the drifting will last. I don't know how to get that.

Answer 1

While "heading" east 2.4 hours at 50 km/h water speed, the boat will have also drifted 20*2.4 = 48 km north due to ocean current in that direction. It will therefore be only 60 - 48 = 12 km south of its destination after 2.4 hours. It only needs to drift with the current another
12 km/20km/h = 0.6 hours (36 minutes) to arrive.

Answer 2

Thanks for the help!