# Linear Equations

Linear Equations
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 1 Linear Equation: Definition 2 Understanding Linear Equation 3 Linear Equation: Formula 4 Linear Equation: Examples 5 How to solve Linear Equations? 6 Thinking out of the Box! 7 Solved Examples on Linear Equation 8 Important Notes on Linear Equation 9 Practice Questions on Linear Equation 11 Maths Olympiad Sample Papers 10 Important Topics of Linear Equation 12 Frequently Asked Questions (FAQs)

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## Linear Equation: Definition

A mathematical statement that has an equal to "=" symbol is called an equation.

Linear equations are equations with degree 1

## Understanding Linear Equation

Appu created a game called "Mind Reader".

He wants to play it with his friends.

He asks one of his friends, Kaira, to think of a number, multiply it by 2 and subtract 5 from it.

He asks her the final result.

Kaira says, "it is 13" Appu instantly says that the number Kaira thought of initially was 9

Kaira nods and Appu's friends including Kaira are surprised!

Everybody wants to know how the game "Mind Reader" works.

Do you know how it works?

By the end of this short lesson, you will understand how it works.

## Linear Equation: Formula

The standard form of a linear equation with variables $$x$$ and $$y$$ is:
 $$Ax+By=C$$ ## Linear Equation: Examples

A linear equation can be written in different ways.

Look at the following equations.

Equations Linear or Non-Linear
1. $$y=8x-9$$ Linear
2. $$y=x^2-7$$ Non-Linear
3. $$\frac{x}{5}=4$$ Linear
4. $$\sqrt{y}+x=6$$ Non-Linear
5. $$y+3x-1=0$$ Linear
6. $$y^3-x=9$$ Non-Linear

### Linear Equations on Graph

The graph of a linear equation in one variable $$x$$ forms a vertical line parallel to $$y$$-axis and vice-versa.

The graph of a linear equation in two variables $$x$$ and $$y$$ forms a straight line. The reason an equation of degree one is called a linear equation is that its geometrical representation is a straight line.

Explore the graphs of linear equations using the simulation below.

## How to Solve Linear Equations?

An equation is like a weighing balance with equal weights on both sides. If we add or subtract the same number from both sides of an equation, it still holds.

Similarly, if we multiply or divide the same number on both sides of an equation, it still holds.

Consider the equation, $$3x-2=4$$ We will perform mathematical operations on the LHS and the RHS so that the balance is not disturbed.

Let's add 2 on both sides to reduce the LHS to $$3x$$

This will not disturb the balance.

The new LHS is $$3x-2+2=3x$$ and the new RHS is $$4+2=6$$ Now let's divide both sides by 3 to reduce the LHS to $$x$$

Thus, we have $$x=2$$  Think Tank
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## Linear Equation: Problems and Solutions

 Example 1

A one-day International cricket match was organised in Nagpur.

India and Sri Lanka were the two teams.

Two Indian batsmen together scored 189 runs. Can you express this information in the form of a linear equation?

Solution:

Let us use the variables $$x$$ and $$y$$ to denote the number of runs scored by each batsmen.

We know that they scored 189 runs together.

Thus, the total of $$x$$ and $$y$$ is 189

 $$\therefore x+y=189$$
 Example 2

Bansi loves to collect two-rupee and five-rupee coins in her piggy bank. She knows that the total sum in her piggy bank is Rs. 77 and it has 3 times as many two-rupee coins as five-rupee coins in it.

She wants to know the exact number of two-rupee coins and five-rupee coins in her piggy bank.

Can you help her find the count?

Solution:

Let the number of five-rupee coins be $$x$$.

The number of two-rupee coins will be $$3x$$

Total amount = $$(5\times x)+(2 \times 3x)$$ According to the information we have,

\begin{align}(5\times x)+(2 \times 3x)&=77\\5x+6x&=77\\11x&=77\\x&=7\end{align}

 $$\therefore$$ She has 7 five-rupee & 21 two-rupee coins

### Linear Equation: Calculator

Try solving linear equations in one variable in the simulation below.

More Important Topics
Numbers
Algebra
Geometry
Measurement
Money
Data
Trigonometry
Calculus