Chapter I : Linear Equations in two variables in two variables

Example 17. A person can row downstream 20 km in 2 hours and upstream 4 km in 2 hours. Find man’s speed of rowing is still water and the speed of the current.

Solution:- Let man’s speed of rowing be x km/h and speed of the current y km/h

Down stream speed = x + y
and upstream speed = x - y

Or, x + y = 10 -------------------(1)

and (x - y) x 2 = 4

Or, x - y = 2 ---------------------(2)

Adding (1) and (2) we get 2x = 12 Or, x = 6

Putting x = 6 in (1) we get 6 + y = 10 Or y = 4

Speed of man =6km/h and speed of current =4km/h

 

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Subjects Maths (Part-1) by Mr. M. P. Keshari
Chapter 1 Linear Equations in Two Variables
Chapter 2 HCF and LCM
Chapter 3 Rational Expression
Chapter 4 Quadratic Equations
Chapter 5 Arithmetic Progressions
Chapter 6 Instalments
Chapter 7 Income Tax
Chapter 8 Similar Triangles