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

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

Math short tricks For competititve Exams | Boat and stream short tricks for UPSC, SSC, RLY and Bank Exam
Short Tricks of Math Boat and Stream

Downloadpdfnotes provides you important notes of math (Boat and Stream) For upcoming Exam. Here you will get new notes of math for competitive exams (UPSC, SSC, Railway, Bank, Police and other exams).

Most Important notes of Math (Boat and Stream) in Hindi and English PDF

Always keep in mind

I. Downstream speed is always greater than the upward speed.
II. Speed of boat is always greater than the speed of the stream.

New Tips and Tricks for Finding Speed of Boat

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
Correct answer: D

Trick: Using Man’s Still Water Speed, Calculate Stream’s Speed

Sailor can row 6 km/h in still water. It takes him 2 times as long to row up as to row down the river. What wil be the speed of the stream.

I. 6 km/ hr
II. 5 km/ hr
III. 3 km/ hr
IV. 2 km/ hr

Let sailor’s speed in upstream = x
Downstream speed = 2x (As given in the question, his downstream speed is 2 times of upstream speed)
Man’s speed in still water = 1/2 (Upstream speed + Downstream speed)
= 1/2 (x + 2x) = 3x/2
3x/2 = 6 (sailor can row 6 km/h in still water)
x = 4 km/hr
Therefore, upstream speed = x = 4 km/hr
Downstream speed = 2x = 2 * 4 = 8 km/hr
Speed of stream = 1/2* (Downstream speed – Upstream speed)
= 1/2 (8 – 4)
= 2 km/hr
Correct answer: D

A man can row a boat 9 km/h in still water. He takes twice the time to move upstream than to move the downstream – the same distance. What will be the speed of the stream.

Let the downward time = 1 hour and so the upward time = 2 hrs.
1/9+s = 2/9-s (Since distance is the same)
18 + 2 s = 9 – s (By cross multiplication)
18 – 9 = s + 2 s
9 = 3 s
Hence s or Speed of stream = 9/3

Answer: 3 km/h
OR
Simply
b + s = 2(b –s)
i.e. b + s = 2b – 2s
i.e. s + 2s = 2b –b
b = 3s or 9 = 3s (b = 9 is given)

Answer-3 km/h