GreenlightTestPrep wrote:
5x + 11y < 0
4x + 10y < 0
Quantity A |
Quantity B |
x + y |
0 |
A) The quantity in Column A is greater.
B) The quantity in Column B is greater.
C) The two quantities are equal.
D) The relationship cannot be determined from the information given.
I created this question to highlight an important property of inequalities.
If two inequalities are such that their inequality symbols are facing the same direction, then we can ADD those inequalities, but we can't subtract those inequalities
In other words, we can't subtract the bottom inequality from the top inequality to get the very convenient inequality x + y < 0 There are several values of x and y that satisfy BOTH given inequalities. Here are two such cases:
Case a: x = -1 and y = -1. In this case, x + y = (-1) + (-1) = -2, which means
Quantity B is greater than Quantity ACase b: x = 5 and y = -3. In this case, x + y = 5 + (-3) = 2, which means
Quantity A is greater than Quantity BAnswer: D