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# Use of Variables

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Variables are used to frame rules to find the perimeter of a polygon. The perimeter of a polygon can be obtained by adding the lengths of its sides.

The following are some simple rules for the properties of numbers using variables.
This property states that two numbers can be added in any order. If a and b represent any two numbers, then a + b = b + a.

Commutative property of multiplication:
This property states that two numbers can be multiplied in any order. If a and b represent any two numbers, then a x b = b x a.

This property states that three numbers can be added in any order.  If a, b and c represent any three numbers, then (a + b) + c = a + ( b + c).

Associative property of multiplication:
This property states that three numbers can be multiplied in any order.  If a, b and c represent any three numbers, then (a x b) x c = a x ( b x c).

Distributive property of multiplication over addition:
This property states that if a, b and c represent any three numbers, then a x ( b + c) = a x b + a x c.

Expressions with variables
1)  5 added to y can be expressed as y + 5.

2) a multiplied by 8 can be expressed as 8a.

3) x divided by 3 can be expressed as $\frac{\text{x}}{\text{3}}$

4) First z multiplied by 2, then 5 substracted from the product can be expressed as 2z - 5.

Using expression practically
1) Saritha has 15 more pens than ameena.

let ameena have x pens then Saritha has x + 15 pens.

2) Raghu's father's age is 2 years more than 3 times Raghu's age.

Let Raghu's age be t years then Raghu's father's age is (3t + 2) years.

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### 2 . WHAT IS THE VALUE OF PIE

it is 22/7.. i think you should know this in class 6 :P

### 3 . Mark scored by Shveta are 10 more than twice the marks scored by Reena.

Marks scored by Reena=x. 10+10=20. ( R)=20x Therefore Sheva's marks=20x. 10+2x=29

### 4 . What is algebra

Algebra is the branches of mathematics. It consists of variables and numbers. e.g 2m

### 5 . dear maam , if the question is - show expression , v multipied by -8 then subtracted from 26 ? ans is 26- -8v ? but the variable always comes before ??

26-(-8v)=26+8v
This can also be written as 8v+26.(commutative property of addition)
But I am a boy not a girl.

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