The maximum value of variable y is 5 more than half of another number z. Which of the following inequalities...
GMAT Algebra : (Alg) Questions
The maximum value of variable y is 5 more than half of another number z. Which of the following inequalities represents all possible values of y?
- \(\mathrm{y \leq \frac{1}{2}z - 5}\)
- \(\mathrm{y \geq \frac{1}{2}z - 5}\)
- \(\mathrm{y \leq \frac{1}{2}z + 5}\)
- \(\mathrm{y \geq \frac{1}{2}z + 5}\)
1. TRANSLATE the maximum value concept
- Given information: 'The maximum value of variable y is...'
- What this tells us: If y has a maximum value, then y cannot be greater than this value
- This means we need the inequality symbol \(\leq\) (less than or equal to)
2. TRANSLATE the expression for the maximum value
- The phrase: '5 more than half of another number z'
- Break it down:
- 'Half of another number z' = \(\frac{1}{2}\mathrm{z}\)
- '5 more than' this quantity = \(\frac{1}{2}\mathrm{z} + 5\)
- So the maximum value is \(\frac{1}{2}\mathrm{z} + 5\)
3. INFER the complete inequality relationship
- Since y cannot exceed its maximum value: \(\mathrm{y} \leq \mathrm{maximum\ value}\)
- Substituting our expression: \(\mathrm{y} \leq \frac{1}{2}\mathrm{z} + 5\)
- This matches choice (C)
Answer: C
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak TRANSLATE skill: Students misinterpret '5 more than' as subtraction instead of addition, thinking it means '5 less than half of z' and writing \(\frac{1}{2}\mathrm{z} - 5\).
This leads them to select Choice A (\(\mathrm{y} \leq \frac{1}{2}\mathrm{z} - 5\)) because they correctly understand that maximum value requires \(\leq\), but they get the expression wrong.
Second Most Common Error:
Weak INFER skill: Students correctly translate the expression to \(\frac{1}{2}\mathrm{z} + 5\), but confuse what 'maximum value' means for the inequality direction. They think 'maximum' means y should be greater than or equal to this value.
This may lead them to select Choice D (\(\mathrm{y} \geq \frac{1}{2}\mathrm{z} + 5\)).
The Bottom Line:
This problem tests both translation skills (converting words to math) and logical reasoning about what 'maximum value' means for constraining a variable. Students need to be careful with both the arithmetic translation and the inequality direction.