Which of the following inequalities, where x is an integer, is/are satisfied by the solution set x = 3, 4, 5? (I) 3x > 9 (II) x − 1 ≥ 2 (III) x + 3 ≥ 5
Which of the following inequalities, where x is an integer, is/are satisfied by the solution set x = 3, 4, 5? (I) 3x > 9 (II) x − 1 ≥ 2 (III) x + 3 ≥ 5 Correct Answer II and III only
Calculation
Given:
(I) 3x > 9
Divide by 3 in above inequality (Here 3 is a positive number so the direction of the inequality does not change)
⇒ x > 9/3
⇒ x > 3
∴ Solution set is (3, ∞)
It doesn’t satisfied the given solution set x = 3
So, statement 1 is wrong.
(II) x − 1 ≥ 2
⇒ x ≥ 2 + 1
⇒ x ≥ 3
∴ Solution set is [3, ∞)
It satisfied the given solution set.
So, statement 2 is correct.
(III) x + 3 ≥ 5
⇒ x ≥ 5 – 3
⇒ x ≥ 2
∴ Solution set is [2, ∞)
It satisfied the given solution set.
So, statement 3 is correct.
Alternate solution:
Consider the given three inequalities for the solution set x = 3, 4, 5
Therefore, substituting 3 in all the three inequalities
1) 3x > 9
⇒ 9 > 9
So, it is false (9 = 9 and is not greater the 9)
2) x – 1 ≥ 2
⇒ 2 ≥ 2
Hence it is true.
3) x + 3 ≥ 5
⇒ 6 ≥ 5
Hence the inequality is true.
For x = 4, 5 inequality II and III are satisfied
Hence, the answer is option 3.