## Boats and Streams

#### Boats and Streams

1. 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 ?

1. ∵ 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

##### Correct 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

1. A man rows downstream 60 km and upstream 36 km, taking 4 hours each time. The speed of the man is :

1. Sd = 15 km/h
Su = 9 km/h
Speed of man= (Sd + Su)/2

##### Correct Option: D

Sd = 15 km/h
Su = 9 km/h
Speed of man= (Sd + Su)/2
∴ Speed of man = (15 + 9)/ 2 = 12 km/h

1. A man can row upstream at 15 km/h and downstream at 21 km/h. The speed of water current of the river is ?

1. Speed of water current =( Vd - Vu)/2

##### Correct Option: C

Speed of water current =( Vd - Vu)/2
= (21 - 15) /2
= 3 km/h

1. 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 ?

1. ∵ Speed of current = 8 - 36/6 = 2 km/hr
⇒ Rate downstream = (8 + 2) = 10 km/hr

##### Correct 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

1. 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 ?

1. 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

##### Correct 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