Boats and Streams
 A man can row upstream 32 km in 4 hours. If the speed of current is 2 km/hr, find how much he can go downstream in 6 hours ?

View Hint View Answer Discuss in Forum
∵ Upstream rate = 32/4 = 8 km/hr
⇒ Speed of man in still water = 8 + 2 = 10 km/hr
⇒ Downstream rate = (10 + 2) = 12 km/hrCorrect Option: B
∵ Upstream rate = 32/4 = 8 km/hr
⇒ Speed of man in still water = 8 + 2 = 10 km/hr
⇒ Downstream rate = (10 + 2) = 12 km/hr
Now, the required distance = 12 x 6 = 72 km
 A man rows downstream 60 km and upstream 36 km, taking 4 hours each time. The speed of the man is :

View Hint View Answer Discuss in Forum
S_{d} = 15 km/h
S_{u} = 9 km/h
Speed of man= (S_{d} + S_{u})/2Correct Option: D
S_{d} = 15 km/h
S_{u} = 9 km/h
Speed of man= (S_{d} + S_{u})/2
∴ Speed of man = (15 + 9)/ 2 = 12 km/h
 A man can row upstream at 15 km/h and downstream at 21 km/h. The speed of water current of the river is ?

View Hint View Answer Discuss in Forum
Speed of water current =( V_{d}  V_{u})/2
Correct Option: C
Speed of water current =( V_{d}  V_{u})/2
= (21  15) /2
= 3 km/h
 A man can row upstream 36 m in 6 hours. If the speed of a man in still water is 8 km/hr, find how much he can go downstream in 10 hours ?

View Hint View Answer Discuss in Forum
∵ Speed of current = 8  36/6 = 2 km/hr
⇒ Rate downstream = (8 + 2) = 10 km/hrCorrect Option: D
∵ Speed of current = 8  36/6 = 2 km/hr
⇒ Rate downstream = (8 + 2) = 10 km/hr
∴ Required distance = (8 + 2) x 10 = 100 km
 The speed of a boat downstream is 15 km/hr and the speed of the stream is 1.5 km/hr. The speed of the boat upstream ?

View Hint View Answer Discuss in Forum
Speed of boat in still water = 15  1.5 = 13.5 km/hr
Speed of boat in upstream = 13.5  1.5 = 12 km/hrCorrect Option: C
Speed of boat in still water = 15  1.5 = 13.5 km/hr
Speed of boat in upstream = 13.5  1.5 = 12 km/hr