Question

If a boat goes down stream 72 milesind upstream 60 miles in 6 hours, the rate of the river and the rate of the boat in still water respectively are

Answer 1

Speed of boat in still water = 11 miles per hour.

Explanation:

Speed = distance / time

or

Distance= Speed * time

Let s be speed of the boat upstream and r be the speed of the river.

Then

Upstream speed= s- r = 60/6= 10 miles per hour

Downstream speed= s+r= 72/6= 12 miles per hour

Therefore

s-r= 10--------- equation A

s+r= 12--------- equation B

Adding equation A and Eq. b

s-r= 10--------- equation A

s+r= 12--------- equation B

2s = 22

or

s= 22/2= 11 miles per hour.

Speed of boat in still water = 11 miles per hour.