NCERT Exemplar Solutions
Class 6 - Mathematics - Unit 7: Algebra - Problems and Solutions
Question 88

Question. 88

If m is a whole number less than 5, complete the table and by inspection of the table, find the solution of the equation 2m − 5 = −1 :

m	0	1	2	3	4
2m−5	−5	−3	−1	1	3

Solution is m = 2

Goal: We want to find the value of m (a whole number less than 5) that makes the equation true:

Left side: (2m - 5)
Right side: (-1)

Meaning: A “solution” is the value of (m) for which the left side becomes exactly (-1).

(m)	0	1	2	3	4
(2m - 5)	(-5)	(-3)	(-1)	(1)	(3)

For (m = 0):
Compute (2m): (2 imes 0 = 0)
Now (2m - 5): (0 - 5 = -5)
Compare with (-1): (-5 eq -1) → Not a solution.
For (m = 1):
Compute (2m): (2 imes 1 = 2)
Now (2m - 5): (2 - 5 = -3)
Compare with (-1): (-3 eq -1) → Not a solution.
For (m = 2):
Compute (2m): (2 imes 2 = 4)
Now (2m - 5): (4 - 5 = -1)
Compare with (-1): (-1 = -1) → This matches!
For (m = 3):
Compute (2m): (2 imes 3 = 6)
Now (2m - 5): (6 - 5 = 1)
Compare with (-1): (1 eq -1) → Not a solution.
For (m = 4):
Compute (2m): (2 imes 4 = 8)
Now (2m - 5): (8 - 5 = 3)
Compare with (-1): (3 eq -1) → Not a solution.

The only value that makes the left side equal to the right side is:

Solution: (m = 2)