Class 7 Maths Chapter 4 Question Answers - Simple Equations

Q1. Check whether the value given in brackets is Solution to the given equation or not
(a) n − 9 = 19 (n = 10)
Ans:
Putting n=10 in LHS
n − 9 = 10 − 9 = 11 ≠ 9
n = 10 is not a solution for the given equation n − 9 = 19.

(b) 17n + 5 = 25 (n = 2)
Ans:
Putting n=2 in LHS
17n+5 = 34 + 5 = 39
39 ≠ 25
n = 2  is not a solution for the given equation 17n + 5=25.

Q2. Give the first step to solve the following equations and then solve the equation.
(a) P+9=3
Ans:
Subtracting 9  from both sides, we obtain
P + 9 = 3P + 9 − 9 = 3 − 9
P = −6

(b) a − 12 = 15
Ans:
Adding 12 both sides, we obtain
a − 12 + 12 = 15 + 12a
= 27

Q3. Solve the equation
Ans:

Q4. Solve 2(P + 9) = −4
Ans:
2p + 18 = −4
2p =  −4 − 18
2p = −22
p = −22
2p = −11

Q5. Write an equation and solve the digit 5 is added to 9  times a number: gives you 77.
Ans:
Let the number x
9 times the number =9x
9x + 5 = 77
9x = 77 − 5
9x = 72
x = 72 / 9
x = 8

Q6. In an isosceles triangle base angles are equal if the vertex angle is 50^o. What are base angles?
Ans:
Let us assume the base angles of the isosceles  triangle as x.
We know that
x + x + 50^o = 180^o
2x + 50^o = 180^o
2x = 130^o
x = 130^o/2
x = 65^o

Q7. If Manvita’s age is year less than the thirteen times of her father’s age. Find her age if her father’s age is 32 years.
Ans:
Let’s Manvita’s age = x years.

Q8. Solve a / 6 = 8 / 18.
Ans:


Q9. Solve 0 = 18 + 3(m + 12).
Ans:
0 = 18 + 3(m + 12)
3m = −54
m = −54 / 3
m = −18

Q10. Solve 5 + 6(q − 1) = 36.
Ans:


Q11. Construct 3 equations starting with x = 5.
Ans:
X = 5
Multiplying both sides by 5.
5x = 25..........(i)
Subtract 5 on both sides
5x − 5 = 25 − 5
5x − 5 = 20.................(ii)
Divide both sides by 2
5x − 2 / 2 = 10
5x / 2 − 5 / 2=10..............(iii)
Here (i),(ii) and (iii) are three equations.

Q12. Solve 3m − 18 = 6 by trial and error method.
Ans:
Put m = 1
3(1) − 18 = 6
3 − 18 = 6
−15 ≠ 6
Put m = 2
3(2) − 18 = 6
6 − 18 = 6
−12 ≠ 6
Put m = 6
3(6) − 18 = 6
18−18 = 6
0 ≠ 6
Put m = 8
3(8) − 18 = 6
24 − 18 = 6
6 = 6
m=8 is the solution of the given equation.

Q13. Write equation and solve
(a) Add 4  to one fourth of a number gives 20.
Ans:
Let the number be x.
14x + 4 = 20
Transferring 4 from LHS to RHS.
14x = 20 − 4
14x = 16
Cross multiplying with 4 on both sides, we get
x = 64
(b) If you take away 5 from 5 times a number you get 50.
Ans:
Let the number be y
5y − 5=50
Transferring 5  from LHS to RHS.
5y = 50 + 5
5y = 55
Dividing by 5 on both sides.
y = 555
y = 11

Q14. Solve
(a) 5p / 6 = 5
Ans:
5p / 6 = 30
Multiplying with  6 on both sides.
5p = 30
Dividing by 5 on both sides
p = 30 / 5
p =  6

(b) 2x + 12 = 28
Ans:
2x + 12=28
Transferring 12 from LHS to RHS.
2x = 28 − 12
2x = 16
Dividing by 2 on both sides
x = 8

Q15. Sum of 5 times a number and 12  is 47. Find the number.
Ans:
Let the number be x.
5x+12=47
Transferring 12 from LHS to RHS.
5x = 47−12
5x = 35
Dividing by 5on both sides
x = 35 / 5
x = 7