Class 7 Maths Chapter 4 Simple Equations Exercise 4.3 pdf notes:-
Exercise 4.3 Class 7 maths Chapter 4 Pdf Notes:-
Ncert Solution for Class 7 Maths Chapter 4 Simple Equations Exercise 4.3 Tips:-
As we have seen, while solving equations one commonly used operation is adding or
subtracting the same number on both sides of the equation. Transposing a number
(i.e., changing the side of the number) is the same as adding or subtracting the number
from both sides. In doing so, the sign of the number has to be changed. What applies to
numbers also applies to expressions. Let us take two more examples of transposing.
Adding or Subtracting Transposing
on both sides
(i) 3p – 10 = 5 (i) 3p – 10 = 5
Add 10 to both sides Transpose (–10) from LHS to RHS
3p – 10 + 10 = 5 + 10 (On transposing – 10 becomes + 10).
or 3p = 15 3p = 5 + 10 or 3p = 15
(ii) 5x + 12 = 27 (ii) 5x + 12 = 27
Subtract 12 from both sides Transposing + 12
(On transposing + 12 becomes – 12)
5x + 12 – 12 = 27 – 12 5x = 27 – 12
or 5x = 15 or 5x = 15
We shall now solve two more equations. As you can see they involve brackets, which
have to be solved before proceeding.
FROM SOLUTION TO EQUATION
Atul always thinks differently. He looks at successive steps that one takes to solve an
equation. He wonders why not follow the reverse path:
Equation Solution (normal path)
Solution Equation (reverse path)
He follows the path given below:
Start with x = 5
Multiply both sides by 4, 4x = 20 Divide both sides by 4.
Subtract 3 from both sides, 4x – 3 = 17 Add 3 to both sides.
This has resulted in an equation. If we follow the reverse path with each
step, as shown on the right, we get the solution of the equation.
Hetal feels interested. She starts with the same first step and builds up another
x = 5
Multiply both sides by 3 3x = 15
Add 4 to both sides 3x + 4 = 19
Start with y = 4 and make two different equations. Ask three of your friends to do the
same. Are their equations different from yours?
Is it not nice that not only can you solve an equation, but you can make
equations? Further, did you notice that given an equation, you get one solution;
but given a solution, you can make many equations?
Now, Sara wants the class to know what she is thinking. She says, “I shall take Hetal’s
equation and put it into a statement form and that makes a puzzle. For example, think of a
number; multiply it by 3 and add 4 to the product. Tell me the sum you get.
If the sum is 19, the equation Hetal got will give us the solution to the
puzzle. In fact, we know it is 5, because Hetal started with it.”
She turns to Appu, Ameena and Sarita to check whether they made
their puzzle this way. All three say, “Yes!”
We now know how to create number puzzles and many other similar