Aptitude day 252

Problems on Boats and Streams:

1. A boat running downstream covers a distance of 12km in 3 hours while covering the same distance upstream, it takes 6 hours. What’s the speed of the boat in the still water?

Solution:

                  Rate of the downstream = 12/3 = 4 km/hr

                  Rate of the upstream = 12/6 = 2 km/hr

                  Speed in the still water = 1/2(4+2) = 3 km/hr.

2. A man goes 1 km against the current of the stream in 1 hour and goes 1 km along the current in 20 minutes. How long will it take to go 8 km in stationary water?

Solution:

                 Rate of the downstream = 1/20*[60] = 3 km/hr.

                 Note: Speed = Distance/ Time and 60 is multiplied for converting minutes to hours

                 Rate of the upstream = 1 km/hr.

                 Speed in still water = 1/2(3+1) = 2 km/hr.

                 Time taken for 8 km = 8/2 = 4 hours.