Detailed Solutions for NCERT Class 7th Mathematics Chapter 4 -Simple Equations Exercise 4.1

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Please find the detailed Solutions for class 7th Maths Chapter 4 Simple Equations Exercise 4.1 Solutions, you can check all the solutions from here chapter wise

NCERT Class 7th Mathematics Chapter 4 Simple Equations Exercise 4.1 Solutions

1. Complete the last column of the table.
Say, whether the equation is satisfied. (Yes/ No)
(i) x + 3 = 0,  x = 3

Sol: Let us put x=3 in the equation

L.H.S. = 3+3 = 6 ≠ R.H.S.

No, the equation is not satisfied.

(ii) x + 3 = 0 x = 0

Sol: Let us put x=0 in the equation

L.H.S. = 0+3 = 3 ≠ R.H.S.

No, the equation is not satisfied.

(iii) x + 3 = 0 x = – 3

Sol: Let us put x= -3 in the equation

L.H.S. = -3+3 = 0 = R.H.S.

Yes, the equation is satisfied.

 (iv) x – 7 = 1 x = 7

Sol: Let us put x=7 in the equation

L.H.S. = 7-7 = 0 ≠ R.H.S.

No, the equation is not satisfied.

(v) x – 7 = 1 x = 8

Sol: Let us put x=8 in the equation

L.H.S. = 8-7 = 1 = R.H.S.

Yes, the equation is satisfied.

(vi) 5x = 25 x = 0

Sol: Let us put x=0 in the equation

L.H.S. = 5*0 = 0 ≠ R.H.S.

No, the equation is not satisfied.

(vii) 5x = 25 x = 5

Sol: Let us put x=5 in the equation

L.H.S. = 5*5 = 25 = R.H.S.

Yes, the equation is satisfied.

(viii) 5x = 25 x = – 5

Sol: Let us put x=-5 in the equation

L.H.S. = 5*-5 = -25 ≠ R.H.S.

No, the equation is not satisfied.

(ix) m/3 = 2 m = – 6

Sol: Let us put m=-6 in the equation

L.H.S. = -6/3 = -2 ≠ R.H.S.

No, the equation is not satisfied.

(x) m/3 = 2 m = 0

Sol: Let us put m=0 in the equation

L.H.S. = 0/3 = 0 ≠ R.H.S.

No, the equation is not satisfied.

(xi) m/3 = 2 m = 6

Sol: Let us put m=6 in the equation

L.H.S. = 6/3 = 2 = R.H.S.

Yes, the equation is satisfied.

2. Check whether the value given in the brackets is a solution to the given equation or
not:
(a) n + 5 = 19 (n = 1)

Sol: Let us put n=1 in the equation

L.H.S. = 1+5 = 6 ≠ R.H.S.

n=1, is not the solution of the given equation.

(b) 7n + 5 = 19 (n = – 2)

Sol: Let us put n=-2 in the equation

L.H.S. = 7*(-2) + 5 = -14+5 = -9 ≠ R.H.S.

n=-2, is not the solution of the given equation.

(c) 7n + 5 = 19 (n = 2)

Sol: Let us put n=2 in the equation

L.H.S. = 7*2+5 = 14+5 =19 = R.H.S.

n=2, is the solution of the given equation.

(d) 4p – 3 = 13 (p = 1)

Sol: Let us put p=1 in the equation

L.H.S. = (4*1)-3 = 4-3 = 1 ≠ R.H.S.

p=1, is not the solution of the given equation.

(e) 4p – 3 = 13 (p = – 4)

Sol: Let us put p=-4 in the equation

L.H.S. = 4*(-4)-3 = -16-3 = -19 ≠ R.H.S.

n=1, is not the solution of the given equation.

(f) 4p – 3 = 13 (p = 0)

Sol: Let us put p=0 in the equation

L.H.S. = 4*0-3 = 0-3 = -3 ≠ R.H.S.

p=0, is not the solution of the given equation.

3. Solve the following equations by trial and error method:
(i) 5p + 2 = 17

Sol: Putting p=1

5*1 + 2 = 5+2= 7 ≠ R.H.S.

Putting p=2

5*2 + 2 = 10+2= 12 ≠ R.H.S.

Putting p=3

5*3 + 2 = 15+2= 17 = R.H.S.

So, p=3 is the solution of the equation.

(ii) 3m – 14 = 4

Sol: Putting m=4

3*4 – 14 = 12-14 = -2 ≠ R.H.S.

Putting m=5

3*5 – 14 = 15-14 = 1 ≠ R.H.S.

Putting m=6

3*6 – 14 = 18-14 = 4 = R.H.S.

So, m=6 is the solution of the given equation.

4. Write equations for the following statements:
(i) The sum of numbers x and 4 is 9.

Ans: x+4 = 9

(ii) The difference between y and 2 is 8.

Ans: y-2 = 8

(iii) Ten times a is 70.

Ans: 10a = 70

(iv) The number b divided by 5 gives 6.

Ans: b/5 = 6

(v) Three fourth of t is 15.

Ans: (3/4)*t = 15

(vi) Seven times m plus 7 gets you 77.

Ans: 7m+7 = 77

(vii) One fourth of a number minus 4 gives 4.

Ans: (1/4)x-4 = 4

(viii) If you take away 6 from 6 times y, you get 60.

Ans: 6y-6 = 60

(ix) If you add 3 to one third of z, you get 30.

Ans: (1/3)z+3 = 30

5. Write the following equations in statement forms:
(i) p + 4 = 15

Ans: The sum of p and 4 is 15

(ii) m – 7 = 3

Ans: 7 subtracted from m is 3

(iii) 2m = 7

Ans: Twice of a number m is 7

(iv) m/5 = 3

Ans: One fifth of a number is 3

(v) 3m/5 = 6

Ans: Three fifth of a number is 6

(vi) 3p + 4 = 25   

Ans: Three times of p when added to 4 is 25

(vii) 4p – 2 = 18

Ans: 4 subtracted from Four times of p is 18

(viii) p/2 + 2 = 8

Ans: 2 added to half of a number p is 8

6. Set up an equation in the following cases:
(i) Irfan says that he has 7 marbles more than five times the marbles Parmit has.
Irfan has 37 marbles. (Take m to be the number of Parmit’s marbles.)

Sol: Let Parmit has m marbes

Then Irfan has 7 marbles more than five times the marbles Parmit has

So Irfan has 5m+7 marbles.

But Irfan Has 37 marbles

So, 5m+7 = 37


(ii) Laxmi’s father is 49 years old. He is 4 years older than three times Laxmi’s age.
(Take Laxmi’s age to be y years.)

Sol: Let the age of Laxmi = y 

Then his father’s age = 3y+4

But his father’s age is 49 years

So, 3y+4 = 49

(iii) The teacher tells the class that the highest marks obtained by a student in her
class is twice the lowest marks plus 7. The highest score is 87. (Take the lowest
score to be l.)

Sol: Let the lowest marks be l

2*Lowest marks + 7 = Highest marks

2*l  + 7 = 87

So, 2l+7 = 87

(iv) In an isosceles triangle, the vertex angle is twice either base angle. (Let the base
angle be b in degrees. Remember that the sum of angles of a triangle is 180
degrees).

Sol: In an isosceles triangle 2 angles are of equal measure

Let base angle = b

Vertex angle = 2* base angle = 2b

Now, in a triangle sum of all angles = 180

b+b+2b = 180 degrees

4b = 180 degrees

You can find the solutions for previous exercise from here