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Question:y gt -4x + 15For which of the following tables are all the values of x and their corresponding values...

GMAT Algebra : (Alg) Questions

Source: Prism
Algebra
Linear inequalities in 1 or 2 variables
HARD
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Notes
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Question:
\(\mathrm{y \gt -4x + 15}\)

For which of the following tables are all the values of x and their corresponding values of y solutions to the given inequality?


  1. xy
    -225
    016
    110
  2. xy
    -223
    016
    112
  3. xy
    -225
    016
    112
  4. xy
    -224
    010
    112
A
xy
-225
016
110
B
xy
-223
016
112
C
xy
-225
016
112
D
xy
-224
010
112
Solution

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.

Answer Choices Explained
A
xy
-225
016
110
B
xy
-223
016
112
C
xy
-225
016
112
D
xy
-224
010
112
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