9.2 Use of Simultaneous Linear Equations

Example Find two numbers whose sum is 70 and difference is 10.

Solution : You are looking for two numbers.

Let the two numbers be x and y. (x > y)

Now we set up two equations from the two conditions given in the problem.

x - y = 10
___________
2x = 80           \ x = 40

Now, substituting in (1), we get 40 + y = 70 \ y = 30

Example The difference between two numbers is 8 and 10 times the smaller number and is equal to eight times the greater. Find the smaller number.

Solution : Let the greater number be x and the smaller number be y.

From the given conditions we set two equations as

[next page]

Index

9.1 - Definition and Solving Techniques
9.2 - Use of Simultaneous Linear Equations

Chapter 1