Question

In one hour a boat goes 11 km long the stream and 5 km against the stream.the speed of the boat in still water is?

Answer 1

by using the concept of relative velocity in upstream and downstream we can get the equations ,

b/r=boat w.r.t. river, r/g=river w.r.t. ground,
V=velocity

V(b/r) + V(r/g) = 11/1 (equation for downstream)

V(b/r) - V(r/g) = 5/1 (equation for upstream)

adding 1st and 2nd equation,
2V(b/r)=16
V(b/r)=8kmph= velocity of boat in still water.