Question

a boy can swim in still water at 4.5 km/h, but takes twice as long to swim upstream than downstream. the speed of the stream is ?

Answer 1

V = speed of boy in still water = 4.5 km/h

v = speed of stream

d = distance traveled

V- v = speed of boy in upstream

V + v = speed of boy in downstream

t₁ = time taken for upstream = d/(V- v)

t₂ = time taken for downstream = d/(V+ v)

given that :

t₁ = 2 t₂

d/(V- v) = 2d/(V+ v)

V + v = 2V - 2v

V = 3v

v = V/3

v = 4.5/3

v = 1.5 km/h