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y lt x^2 + 5 For which of the following tables are all the values of x and their corresponding...

GMAT Algebra : (Alg) Questions

Source: Prism
Algebra
Linear inequalities in 1 or 2 variables
HARD
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Notes
Post a Query

\(\mathrm{y \lt x^2 + 5}\)

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

Choose 1 answer:

A
x y
3 14
5 30
7 54
B
x y
3 10
5 34
7 50
C
x y
3 10
5 26
7 50
D
x y
3 18
5 34
7 58
Solution

1. TRANSLATE the inequality requirement

  • Given: \(\mathrm{y \lt x² + 5}\)
  • This means: For each (x,y) pair, the y-value must be less than \(\mathrm{x² + 5}\)
  • We need ALL pairs in a table to satisfy this condition

2. SIMPLIFY to find the boundary values

  • Calculate \(\mathrm{x² + 5}\) for each x-value:
  • For \(\mathrm{x = 3}\): \(\mathrm{3² + 5 = 9 + 5 = 14}\)
  • For \(\mathrm{x = 5}\): \(\mathrm{5² + 5 = 25 + 5 = 30}\)
  • For \(\mathrm{x = 7}\): \(\mathrm{7² + 5 = 49 + 5 = 54}\)

3. CONSIDER ALL CASES by checking each table systematically

Table A:

  • (3, 14): Is \(\mathrm{14 \lt 14}\)? No ✗
  • Since the first pair fails, Table A is eliminated

Table B:

  • (3, 10): Is \(\mathrm{10 \lt 14}\)? Yes ✓
  • (5, 34): Is \(\mathrm{34 \lt 30}\)? No ✗
  • Since one pair fails, Table B is eliminated

Table C:

  • (3, 10): Is \(\mathrm{10 \lt 14}\)? Yes ✓
  • (5, 26): Is \(\mathrm{26 \lt 30}\)? Yes ✓
  • (7, 50): Is \(\mathrm{50 \lt 54}\)? Yes ✓
  • All pairs satisfy the inequality!

Table D:

  • (3, 18): Is \(\mathrm{18 \lt 14}\)? No ✗
  • Since the first pair fails, Table D is eliminated

Answer: C




Why Students Usually Falter on This Problem

Most Common Error Path:

Weak CONSIDER ALL CASES skill: Students check only the first pair in each table and select based on partial information.

For example, they might check Table A, see that \(\mathrm{14 \lt 14}\) is false, then check Table B, see that \(\mathrm{10 \lt 14}\) is true, and immediately select B without checking the remaining pairs. Since \(\mathrm{34 \lt 30}\) is false, this leads them to select Choice B (Table B).

Second Most Common Error:

Poor TRANSLATE reasoning: Students misinterpret the inequality direction, thinking \(\mathrm{y \gt x² + 5}\) instead of \(\mathrm{y \lt x² + 5}\).

This reversal makes them look for y-values that are greater than the calculated boundary values. Under this misconception, Table A looks perfect since \(\mathrm{14 \geq 14}\), \(\mathrm{30 \geq 30}\), and \(\mathrm{54 \geq 54}\), leading them to select Choice A (Table A).

The Bottom Line:

This problem tests systematic checking skills more than mathematical calculation. Students must resist the urge to jump to conclusions after checking just one or two pairs from each table.

Answer Choices Explained
A
x y
3 14
5 30
7 54
B
x y
3 10
5 34
7 50
C
x y
3 10
5 26
7 50
D
x y
3 18
5 34
7 58
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