Question
Wed April 09, 2014 By: Udit Lilhare

# The question is :-A boat on a river travels downstream between two points 20 km apart in one hour.The return trip against the current taken two and half hours.What is the speed of the boat?(A)8 km/hr  (B)10 km/hr  (C)14 km/hr  (D)16km/hr

Wed April 09, 2014
Important Formulae:
1. Downstream/Upstream:

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

2. If the speed of a boat in still water is u km/hr and the speed of the stream is vkm/hr, then:

Speed downstream = (u + v) km/hr.

Speed upstream = (u - v) km/hr.

3. If the speed downstream is a km/hr and the speed upstream is b km/hr, then:

 Speed in still water = 1 (a + b) km/hr. 2
 Rate of stream = 1 (a - b) km/hr. 2
Solution:         Rate downstream = = 20
 Rate upstream ==8  Speed in still water =(20+8) kmph = 14 km/hr
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