A swimmer can swim in stillwater at a rate 4 kilometre per hour. If he swims in a river flowing at 3 kilometre per hour and keeps his direction with respect to water perpendicular to the current,find his velocity city with respect to the ground

Answer 1

say the water is moving in x direction at 4 km/h
say we swim in y direction at 3 km/h

then our speed is sqrt (3^2+4^2) = 5 km/h

tan angle above x axis is
tan theta = 3/4 = .75