Question

A ship steams due west at the rate of 15 kmph when the river is flowing at the rate 6 kmph due south. What is the velocity relative to the ship of a train going due north at the rate of 30 kmph?

Answer 1

Relative velocity of train with respect to still water = $30-(-6)= 36 \ km\ per \ hr$

Relative velocity of train with respect to ship =

$\sqrt{36^2+ 15^2}=39 \ km \ per\ hr$