GMAT Inequalities: 3 r ≤ 4 s+5 |s| ≤ 5 Given…
Question
3 r ≤ 4 s+5 |s| ≤ 5 Given the inequalities above, which of the following CANNOT be the value of r?
- -20
- -5
- 0
- 5
- 20
Topics: inequalities, absolute values, simultaneous equations
Solution
Step 1
We turn the absolute value condition on s into a range for s.
|s| ≤ 5[[LB]]-5 ≤ s[[LB]]s ≤ 5
Step 2
We isolate r by dividing the inequality 3r ≤ 4s + 5 by the positive number 3.
3r ≤ 4s + 5 r ≤ (4s+5)/3
Step 3
We find the highest bound for r by using the largest s=5.
r ≤ (4×5+5)/3 = 25/3 8.33
Step 4
We compare this bound to each choice and see that 20 exceeds about 8.33.
20 > 25/3 8.33
Answer
20 (E)
