a Boat takes 7 hours to go 70 kilometre downstream and 35 kilometre upstream. It takes 7 hours to go 80 km downstream and 30 km upstream then find the speed of the boat in still water and the speed of the stream
Answers
Step-by-step explanation:
The boat covers the same distance in 4 hours while running downstream. E. km/hr = 8 km/hr. km/hr = 12 km/hr.
Time requires to travel 20 km upstream is 26.67 min .
One can row 10 km in 10 minutes in still water . The same distance in 8 minutes with the stream .
Hence upstream speed = 60 – 15 = 45 km/hr. So time taken to cover 20 km = 20/45*60 = 26.67min.
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is: A. (11 + 5) kmph = 8 kmph.
Step-by-step explanation:
Let the speed of the boat in still water be x kmph, and the speed of the stream be y kmph. Then the net speed of the boat downstream will be x+y kmph while that of upstream will be x-y kmph.
Remembering that the relation between time T speed S and distance D is given by T = D/S we get according to the problem two equations 100/(x+y) + 30/(x-y) = 6………………………(1) and 75/(x+y) + 75/(x-y) = 8.………………………..(2). Putting 1/(x+y) = a and 1/(x-y) = b the above equations reduce to 100 a + 30 b = 6 ………(3) and 75a + 75b = 8 ………………………………….(4) Solving we get a =1/25 and b = 1/15 which means that x+y = 25 and x-y = 15 that by solving these yield x = 20 and y = 5
Hence, speed of boat in still water is 20 kmph and the speed of the stream is 5 kmph.