Boats and Streams Aptitude Questions - Shortcuts, Formulas, Tricks

boat_001Boat And Stream: The water of stream is usually keep, flowing at a certain speed in a particular direction . This Speed is called current of the stream. A boat develops speed because of its engine power .The speed with which it travels when there is no current is called speed of boat in still water . A boat can travels in the direction of current as well as against the current. (as long as speed of boat in still water is greater than the current).

Downstream: when the boat moves in the direction of current is called stream or current or down stream.If a boat or a swimmer swims in the same direction as the stream, then it is called downstream. Obviously the boat or swimmer require less efforts to travel using downstream. Because the stream itself helps the objects to move.

Note: as the object moves along with the water, the stream helps the object. So, the down stream speed (DS) is

DS = U+V where U is the speed of the object in the still water V is the speed of the water.

Upstream: when the boat moves in the direction opposite to the that of the current is called against the stream or against the current or upstream .

Note: as the object moves against the water pushes the object in opposite direction. So, the upstream speed (US) is

US = U-V , where U is the speed of the object in the still water V is the speed of the water.

 

Boats and Streams Important Formulas

1) Let us assume that the speed of the boat in still water is U km/hr and the speed of stream is V km/hr then, as mentioned above :

(a) Speed downstream = (u+v)km/hr
(b) Speed upstream = (u-v)km/hr

2) If the speed downstream is a km/hr and the speed upstream is b km/hr then :
(a) Speed in still water = \frac{1}{2}\left ( a\: +\: b\right ) km/hr
(b) Rate of stream = \frac{1}{2}\left ( a\: -\: b\right ) km/hr

Boats and Streams Solved Examples

Question 1: A boat covers a certain distance downstream in 1 hour, while it comes back in 3/2 hours. If the speed of the stream is 3kmph, what is the speed of the boaat in still water ?

Solution: Let the speed of the boat in still water be x kmph.
then speed downstream = (X+3) kmph
Speed upstraem = (x-3)kmph

\therefore (x+3)\times \; 1=\; (x+3)\times \frac{3}{2} 2x+6 = 3x-9

\Rightarrow 2x+6 = 3x-9 \Rightarrow x = 15kmph

Question 2: A speed of a boat in still water is 10 km/hr. If it can travel 26km downstream and 14km upstream in the same time , the speed of the stream is ?

Solution: Let the speed of the stream be x km/hr. then,

Speed downstream=(10+x)km/hr,

speed upstream= (10-x)km/hr

\therefore \frac{26}{10+x}\: =\: \frac{14}{10-x}

\Rightarrow 260-26x= 140+14x \Rightarrow 40x=120

\Rightarrow x = 3km/hr

Question 3: The speed of the boat in still water is 10km/hr and the rate of the current is 3 km/hr. The distance traveled downstream in 12 minutes is?

Solution: Speed downstream =(10+3) kmph= 13 km/h

Distance traveled = 13\times \frac{12}{16} = 2.4 km/h

Question 4: A man takes twice long to row a distance against the stream as to row the same distance in favor of the stream .the ratio of the speed of the boat in still water is ?

 

Boats and Streams questions from previous year exams

IBPS Questions related to boat and stream.

 

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