# Class 7 Maths Chapter 4 Exercise 4.1 Pdf Notes NCERT Solutions

Class 7 Maths Chapter 4 Simple Equations Exercise 4.1 pdf notes:-

**Exercise 4.1** Class 7 maths Chapter 4 Pdf Notes:-

**To see video Solution Of This Exercise Click Here**

## Ncert Solution for Class 7 Maths Chapter 4 Simple Equations Exercise 4.1 Tips:-

**A MIND-READING GAME!**

The teacher has said that she would be starting a new chapter in

mathematics and it is going to be simple equations. Appu, Sarita

and Ameena have revised what they learnt in algebra chapter in

Class VI. Have you? Appu, Sarita and Ameena are excited because

they have constructed a game which they call mind reader and they

want to present it to the whole class.

The teacher appreciates their enthusiasm and invites them to present their game. Ameena

begins; she asks Sara to think of a number, multiply it by 4 and add 5 to the product. Then,

she asks Sara to tell the result. She says it is 65. Ameena instantly declares that the number

Sara had thought of is 15. Sara nods. The whole class including Sara is surprised.

It is Appu’s turn now. He asks Balu to think of a number, multiply it by 10 and subtract

20 from the product. He then asks Balu what his result is? Balu says it is 50. Appu

immediately tells the number thought by Balu. It is 7, Balu confirms it.

Everybody wants to know how the ‘mind reader’ presented by Appu, Sarita and

Ameena works. Can you see how it works? After studying this chapter and chapter 12,

you will very well know how the game works.

**SETTING UP OF AN EQUATION**

Let us take Ameena’s example. Ameena asks Sara to think of a number. Ameena does not

know the number. For her, it could be anything 1, 2, 3, . . ., 11, . . . , 100, . . . . Let us

denote this unknown number by a letter, say x. You may use y or t or some other letter in

place of x. It does not matter which letter we use to denote the unknown number Sara has

thought of. When Sara multiplies the number by 4, she gets 4x. She then adds 5 to the

product, which gives 4x + 5. The value of (4x + 5) depends on the value of x. Thus

if x = 1, 4x + 5 = 4 ×1 + 5 = 9. This means that if Sara had 1 in her mind, her result would

have been 9. Similarly, if she thought of 5, then for x = 5, 4x + 5 = 4 × 5 + 5 = 25; Thus

if Sara had chosen 5, the result would have been 25.

The word variable means something that can vary, i.e. change. A variable takes on

different numerical values; its value is not fixed. Variables are denoted usually by

letters of the alphabets, such as x, y, z, l, m, n, p, etc. From variables, we form

expressions. The expressions are formed by performing operations like addition, subtraction,

multiplication and division on the variables. From x, we formed the expression (4x + 5).

For this, first we multiplied x by 4 and then added 5 to the product. Similarly, from y, we

formed the expression (10y – 20). For this, we multiplied y by 10 and then subtracted 20

from the product. All these are examples of expressions.