Question

a motorboat takes 4 hours to travel 128 km going Upstream. the return trip takes 2 hours going Downstream. what is the rate of the boat in still water and what is the rate of the current? rate of the boat in still water: __km/hrate of the current: __km/h

Answer 1

Distance = rate * time

r= rate of the boat in still water

c= rate of current

Upstream = r - c

Downstream= r+c

Upstream

r-c = 128/4 = 32

r-c= 32 (a)

Downstream

r+c=128/2=64

r+c=64 (b)

Add both equations (a)+(b)

r-c=32

+

r+c= 64

_______

2r= 96

r= 96/2

r=48 km/h

Substitute r in (b)

48+c =64

c= 64-48

c= 16km/h