Question:y gt -4x + 15For which of the following tables are all the values of x and their corresponding values...
GMAT Algebra : (Alg) Questions
\(\mathrm{y \gt -4x + 15}\)
For which of the following tables are all the values of x and their corresponding values of y solutions to the given inequality?
x y -2 25 0 16 1 10 x y -2 23 0 16 1 12 x y -2 25 0 16 1 12 x y -2 24 0 10 1 12
| x | y |
|---|---|
| -2 | 25 |
| 0 | 16 |
| 1 | 10 |
| x | y |
|---|---|
| -2 | 23 |
| 0 | 16 |
| 1 | 12 |
| x | y |
|---|---|
| -2 | 25 |
| 0 | 16 |
| 1 | 12 |
| x | y |
|---|---|
| -2 | 24 |
| 0 | 10 |
| 1 | 12 |
1. TRANSLATE the problem requirements
- Given: The inequality \(\mathrm{y \gt -4x + 15}\)
- Need to find: Which table has ALL coordinate pairs that satisfy this inequality
- What this means: For each (x,y) pair, when we substitute the values, y must be strictly greater than -4x + 15
2. INFER the solution strategy
- We need to test every single pair in each table systematically
- If even one pair fails the inequality test, that entire table is eliminated
- Only the table where ALL pairs work is correct
3. SIMPLIFY by testing each table systematically
Table A Check:
- For (-2, 25): Is \(\mathrm{25 \gt -4(-2) + 15}\)?
\(\mathrm{25 \gt 8 + 15}\)
\(\mathrm{25 \gt 23}\)? ✓ True - For (0, 16): Is \(\mathrm{16 \gt -4(0) + 15}\)?
\(\mathrm{16 \gt 15}\)? ✓ True - For (1, 10): Is \(\mathrm{10 \gt -4(1) + 15}\)?
\(\mathrm{10 \gt -4 + 15}\)
\(\mathrm{10 \gt 11}\)? ✗ False
Table A fails because 10 is not greater than 11.
Table B Check:
- For (-2, 23): Is \(\mathrm{23 \gt -4(-2) + 15}\)?
\(\mathrm{23 \gt 8 + 15}\)
\(\mathrm{23 \gt 23}\)? ✗ False
Table B fails immediately because 23 is not strictly greater than 23.
Table C Check:
- For (-2, 25): Is \(\mathrm{25 \gt -4(-2) + 15}\)?
\(\mathrm{25 \gt 23}\)? ✓ True - For (0, 16): Is \(\mathrm{16 \gt -4(0) + 15}\)?
\(\mathrm{16 \gt 15}\)? ✓ True - For (1, 12): Is \(\mathrm{12 \gt -4(1) + 15}\)?
\(\mathrm{12 \gt 11}\)? ✓ True
All three pairs work for Table C!
4. CONSIDER ALL CASES by checking Table D for completeness
- For (-2, 24): Is \(\mathrm{24 \gt -4(-2) + 15}\)?
\(\mathrm{24 \gt 23}\)? ✓ True - For (0, 10): Is \(\mathrm{10 \gt -4(0) + 15}\)?
\(\mathrm{10 \gt 15}\)? ✗ False
Table D fails because 10 is not greater than 15.
Answer: C
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak CONSIDER ALL CASES skill: Students often check only the first one or two pairs in each table instead of testing every single pair. For example, they might test Table A's first pair (-2, 25), see that \(\mathrm{25 \gt 23}\) is true, and mistakenly conclude Table A is correct without checking the remaining pairs. This leads them to select Choice A (Table A) even though the third pair (1, 10) actually fails the inequality test.
Second Most Common Error:
Conceptual confusion about strict inequality: Students may not understand that ">" means strictly greater than, not greater than or equal to. When they encounter Table B's first pair where \(\mathrm{23 \gt 23}\), they might think this is acceptable since 23 = 23. This conceptual gap causes them to select Choice B (Table B) instead of recognizing that 23 is not strictly greater than itself.
The Bottom Line:
This problem requires methodical checking of every data point combined with precise understanding of inequality symbols. Students who rush through the checking process or misunderstand the strict nature of ">" will consistently select incorrect answers.
| x | y |
|---|---|
| -2 | 25 |
| 0 | 16 |
| 1 | 10 |
| x | y |
|---|---|
| -2 | 23 |
| 0 | 16 |
| 1 | 12 |
| x | y |
|---|---|
| -2 | 25 |
| 0 | 16 |
| 1 | 12 |
| x | y |
|---|---|
| -2 | 24 |
| 0 | 10 |
| 1 | 12 |