Learning objectives
● To identify variables and constants in the given terms of an algebraic expression.
● To find the coefficients of the terms of an algebraic expression.
● To identify like and unlike terms.
● To add and subtract algebraic expressions with integer co-efficients.
● To form simple expressions in two variables.
● To understand simple linear equations and solve problems.

__Chapter 3__

__ALGEBRA__

** **

**Learning objectives**

● To identify variables and constants in the given
terms of an algebraic expression.

● To find the coefficients of the terms of an algebraic
expression.

● To identify like and unlike terms.

● To add and subtract algebraic expressions with
integer co-efficients.

● To form simple expressions in two variables.

● To understand simple linear equations and solve
problems.

** **

**Recap**

In class VI, we have learnt how geometric patterns
and number patterns can be generalised using variables and constants. A variable
takes different values which is represented by *x,y,z*... and constant has numerical values such as 31,
− 7, 3/10 etc.

For example,

(i) The number of Ice
− candy sticks required to form one square () is four sticks, for two
squares is eight sticks, for three squares is twelve sticks and so on.

Continuing in the same way, it is clear that if
the number of squares () to be formed is *k* (any natural number), then the number of candy sticks required will be
4 × *k* = 4*k*, where k is a variable and 4 is a constant.

This can be observed in the following table:

(ii) Observe the following
pattern

7×9 = 9×7,

23×56 = 56×23,

999 × 888 = 888 × 999

This can be generalised as *a* × *b* = *b* × *a*, where *a,
b* are variables.

** **

**Try these**

**1. Identify the variables and constants among the following terms:**

*a***,11*** ***−*** ***3***x***, xy, **

** Variables :** a, –3x, xy, –m, n,
5ab, 3y, 8 pqr, –9t

** Constants :** 11, –89, 5, –5,
18,–1, –8

**2. Complete the following table:**

**Note :**** ****Algebraic statements are also known
as Algebraic expressions.**

__Introduction__

Consider the situation. Murugan’s mother gave him
₹100
to buy 1 kilogram of sugar. If the shopkeeper returned ₹58,
what is the price of sugar?

Let us see another situation. Jayashri wants to
share chocolates among her friends on her birthday. She had ₹190
in her piggy bank. If she could buy 95 chocolates with that amount, then what is
the price of one chocolate?

Did you get the answers? How did you work out?

You might have created numeric equations like 100
– 58 = ? and 190 ÷ 95 = ? and then solved it. Isn’t it? In both the cases, question
mark (?) stands for an unknown value. Instead of using question marks everytime,
we could use the letters like *x, y, a, b*
…

Let us learn more about this interesting branch
of mathematics which deals with the methods of finding the unknown values.

** **

**MATHEMATICS ALIVE - ALGEBRA IN REAL LIFE**

Tags : Term 1 Chapter 3 | 7th Maths , 7th Maths : Term 1 Unit 3 : Algebra

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