## Boats and Streams

#### Boats and Streams

1. A boat goes 14 km upstream in 56 minutes. The speed of stream is 2 km/hr. The speed of boat in still water is ?

1. ∵ Speed upstream = 14 x (60/56) = 15 km/hr
Speed in upstream = Speed in still water - Speed of stream.

##### Correct Option: D

∵ Speed upstream = 14 x (60/56) = 15 km/hr
Speed in upstream = Speed in still water - Speed of stream.
⇒ x - 2 = 15
∴ x = 17 km/hr

1. The speed of a boat in still water is 10 km/hr. If its speed down stream be 13 km/hr, then speed of the stream is ?

1. Speed in still water + Speed of stream = Speed in downstream.
⇒ 10 + y = 13

##### Correct Option: B

Speed in still water + Speed of stream = Speed in downstream.
⇒ 10 + y = 13
∴ y = 13 - 10 = 3 km/hr

1. The speed of a boat in still water is 12 km per hour. Going downstream it moves at the rate of 19 km per hour. The speed of the boat against the stream is ?

1. Speed of stream = speed in downstream - Speed in still water
⇒ Speed of stream = 19 - 12 = 7 km/hr

Speed of boat against stream = Speed in still water - Speed of stream.
⇒ Speed of boat against stream = 12 - 7 = 5 km/hr

##### Correct Option: A

Speed of stream = speed in downstream - Speed in still water
⇒ Speed of stream = 19 - 12 = 7 km/hr

Speed of boat against stream = Speed in still water - Speed of stream.
⇒ Speed of boat against stream = 12 - 7 = 5 km/hr

1. If a man rows at the rate of 5 km/hr in still water and his rate against the current is 3.5 km/hr, then the man's rate along the current is ?

1. Speed of current = 5 - 3.5 = 1.5 km/hr
Man's speed along the current = Man speed in still water + speed of current.

##### Correct Option: B

Speed of current = 5 - 3.5 = 1.5 km/hr
Man's speed along the current = Man speed in still water + speed of current.
⇒ Man's speed along the current = 5 + 1.5 = 6.5 km/hr

1. A man rows upstream 16 km and downstream 27 km talking 5 hours each time. What is the velocity of current ?

1. ∵ Man's rate upstream = 16/5 km/hr
Man's rate downstream = 27/5 km/hr

##### Correct Option: C

Man's rate upstream = 16/5 km/hr
Man's rate downstream = 27/5 km/hr

∴ Velocity of the current = (27/5 - 16/5)/2 km/hr = 1.1 km/hr