Aptitude Day 253

Problems on Boats and Streams:

1. A man takes thrice as long to row a distance against the stream as to row the same distance in favour of the stream. The ratio of the speed of the boat in still water and the stream is:

Solution:

                 (3x+x)/2 : (3x-x)/2 = 4x/2: 2x/2

                                                = 2:1.

2. A boat running upstream takes 11 hours 30 minutes to cover a certain distance, while it takes 5 hours to cover the same distance in the downstream. What’s the ratio between the speed of the boat and the speed of the water current respectively?

Solution:

                 x*11(1/2) = 5y ----- Equation 1

                 From equation 1, we get

                 y = 11x/10

                 The ratio is (y+x)/2 : (y-x)/2 = (21x/10 *1/2) : (x/10*1/2) 

                                                                = 21: 1.