Boat and Streams

Boat and Streams

Downstream
In water, the direction along the stream is called downstream.
 
Upstream
In water, the direction against the stream is called upstream.
 

Some Basic Formulas:

1. Let the speed of a boat in still water be u km/hr and the speed of the stream be v km/hr, then 
Speed downstream = (u + v) km/hr 
Speed upstream = (u - v) km/hr
 
2. Let the speed downstream be a km/hr and the speed upstream be b km/hr, then
Speed in still water=
Rate of stream=
3. A man can row in still water at x km/h. In a stream flowing at y km/h, if he rows the same distance up and down the stream, then his average speed is given by
4. Let the speed of a man in still water be x km/hr and the speed of a stream be y km/hr. If he takes t hours more in upstream than to go downstream for the same distance, the distance 
 
5. A man can row a boat in still water at x km/hr. In a stream flowing at y km/hr, if it takes him t hours to row a place and come back, then the distance between the two places 
 
6. A man can row certain distance downstream in t1 hours and returns the same distance upstream in t2 hours. If the speed of stream is y km/h, then the speed of man in still water is given by
 
7. A man takes n times as long to row upstream as to row downstream the river. If the speed of the man is x km/hr and the speed of the stream is y km/hr, then 

Questions Asked from this Chapter:

Question Type 1: A Boat/Man covers X1 Km upstream and Y1 Km downstream in H1 hours while it covers X2 Km upstream and Y2 Km downstream in H2 hours. Find Speed of Boat & Stream

Example:

The speed of a boat in still water is 10 Km/hr. It covers upstream a distance of 45 Km in 6 hours. The speed(in Km/hr) of stream is:
a) 2.5
b) 3
c) 3.5
d) 4
Solution:
 

Question Type 2: A Boat/Man goes X Km upstream in H1 hours and Y Km downstream in H2 hours. Find Speed of Boat & Stream 

Example:

A sailer goes 12 Km downstream in 48 minutes and return in 1 hour 20 minutes. The speed of the sailer in still water is:
a) 12 Km/hr 
b) 12.5 Km/hr
c) 13 Km/hr
d) 15 Km/hr
Solution:
 

Question Type 3: A Boat/Man takes 'N' times as much time in going the same distance in opposite direction.

Example:
In a fixed time, a boy swims double the distance along the current that he swims against the current. If the speed of the current is 3 km/hr, the speed of the boy in still water is:
a) 6 Km/hr
b) 9 Km/hr
c) 10 km/hr
d) 12 km/hr
Solution: