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Boat and Stream Tricks: Short Tricks of Math Boat and Stream For Commpetitive Exams

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Boats and Streams Shortcuts

  • I.    Speed of the boat in still water = 1/2 (Downstream speed + Upstream speed)
  • II.    Downstream speed = Speed of boat in still water + Speed of stream
  • III.    Upstream speed = Speed of boat in still water – Speed of stream

A boy rows a boat at 12 km/h along the stream and 8 km/h against the stream. Now what is the speed of the boat in still water.

  • I.    12km/hr
  • II.    10km/hr
  • III.    15km/hr
  • IV.    8km/hr

Solution-

  • Downstream speed of the boat – 12 km/h
  • Upstream speed of the boat – 8 km/h

Speed of the boat in still water – ½ (Downstream speed + Upstream speed)
= 1/2 (12 + 8)
= 10 km/h
Correct answer: B

Problem on boat and Stream

Trick- Shortcuts for Boats and Streams

Speed of stream = 1/2 *(Downstream speed – upstream speed)

  • I.    Speed upstream = (u – v )km/hrs
  • II.    Speed downstream = (u + v ) km/hr

A boat whose speed in 15 km/hr in still water goes 30 km downstream and it takes 4.5 hrs to come back. What will be the speed of the stream

  • I.    A . 25km/hr
  • II.    B. 15m/hr
  • III.    C. 20km/hr
  • IV.    D. 5km/hr

Solution:     
Let the speed of stream = x
Therefore, speed downstream = 15 + x
Speed upstream = 15 – x
30/(15+x) + 30/(15-x) = 4hr 30 min
30/(15+x)+ 30/(15-x) = 9/2
Finaly
x = 5km/hr

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