CBSE NCERT Solutions for Class 7 Chapter 4

The solutions for class 7 provide students a fine preparation strategy in order to prepare for their exam more methodically. Students get a fair idea on the subject, the sort of questions that are possibly asked and the method to answer them.

CBSE NCERT Solutions for Class 7 Maths Chapter 4:

Question-1:

Check whether the value given in the brackets is a solution to the given equation or not:
(a) n+5=19(n=1)
(b) 7n+5=19(n=-2)
(c) 7n+5=19(n=2)
(d) 4p-3=13(p=1)
(e) 4p-3=13(p=-4)

Solution:

(a) n+5=19(n=1)
Putting n=1 in L.H.S.,
1+5=6
∵ L.H.S ≠ R.H.S
∴ n=1 is not the solution of given equation.

(b) 7n+5=19 (n=2)
Putting n=-2 in L.H.S.
7(-2)+5=-14+5=-9
∵ L.H.S ≠ R.H.S
∴ n=-2 is not the solution of given equation.

(c) 7n+5 = 19 (n=2)
Putting n=2 in L.H.S
7(2)+5=14+5=19
∵ L.H.S =R.H.S,
∴ n=2 is the solution of given equation.

(d) 4p-3=13(p=1)
4(1) – 3=4 – 3=1
∵ L.H.S ≠ R.H.S.,
∴ p=1 is not the solution of given equation.

(e) 4p-3=13(p=4)
Putting p = -4 in L.H.S,
4(-4)-3=-16-3=-19
∵ L.H.S ≠ R.H.S.,
∴ p=0 is not the solution of given equation.

Question-2:

Solve the following equations by trial and error method:
(i) 5 p+ 2 = 17
(ii) 3m- 14 = 4

Solution:

(i) Putting p = -3 in L.H.S 5 (-3 ) + 2 = -15 + 2 = -13
∵ -13 ≠ 17 Therefore, , p = -3 is not the solution.
Putting p=-2 in L.H.S 5 (-2) + 2 = -10 + 2 = -8
∵  -8 ≠ 17 Therefore , p=-2 is not the solution.
Putting p=-1 in L.H.S 5(-1)+2=-5+2=-3
∵ -3 ≠ 17 Therefore, p = -1 is not the solution.
Putting p=0 in L.H.S 5(0)+2=0+2=2
∵ 2 ≠ 17 therefore p=0 is not the solution.
Putting p=1 in L.H.S 5(1)+2=5+2=7
∵ 7 ≠ 17 Therefore, p = 1 is not the solution.
Putting p=2 in L.H.S 5(2)+2=5+2=7
∵ 12 ≠ 17 Therefore, p=1 is not the solution.
Putting p=2 in L.H.S 5(2) +2=10+2=12
∵ 12 ≠ 17 Therefore, p=2 is not the solution.
Putting p=3 in L.H.S 5(3)+2=15=17
∵ 17=17 Therefore, p=3 is the solution.

(ii) 3m-14=4
Putting m=-2 in L.H.S 3(-2)-14=-6-14=-20
∵ -20 ≠ 4 Therefore, m=-2 is not the solution.
Putting m=-1 in L.H.S 3(-2) -14=-6-14=-20
∵-20 ≠ 4 Therefore, m=-2 is not the solution.
Putting m=-1 in L.H.S 3(-1) -14=-3-14=-17
∵-17 ≠ 4 Therefore, m = -1 is not the solution.
Putting m=0 in L.H.S 3(0)-14=0-14=-14
∵-14 ≠ 4 Therefore, m=0 is not the solution.
Putting m=1 in L.H.S 3(1)-14=3-14=-11
∵-11 ≠ 4 Therefore, m=1 is not the solution.
Putting m=2 in L.H.S 3(2) -14=6-14=-8
∵-8 ≠ 4 Therefore, m=2 is not the solution.
Putting m=3 in L.H.S 3(3)-14=9-14=-5
∵-2 ≠ 4 Therefore, m=4 is not the solution.
Putting m=5 in L.H.S 3(5)-14=15-14=1
∵1 ≠ 4 Therefore, m=5 is not the solution.
Putting m=6 in L.H.S 3(6)-14=18-14=4
∵ 4=4 Therefore, m=6 is not the solution.