BTGModeratorVI wrote: ↑Thu Jun 18, 2020 5:47 am
Is xy < 10?
1) x < 2
2) y < 5
Answer:
E
Source: Math Revolution
Target question: Is xy< 10?
Statement 1: x < 2
Since there's no information about y, this statement is not sufficient.
However, if we're not certain about this insufficiency, we can TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So,
xy < 10
Case b: x = 1 and y = 20, which means xy = (1)(20) = 1. So,
xy > 10
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: y < 5
Since there's no information about x, this statement is not sufficient.
Let's test some values (for "fun")
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So,
xy < 10
Case b: x = 10 and y = 2, which means xy = (10)(2) = 20. So,
xy > 10
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
There are still several values of x and y that satisfy BOTH statements and yield contradictory answers to the
target question. Here are two:
Case a: x = 1 and y = 1, which means xy = (1)(1) = 1. So,
xy < 10
Case b: x = -5 and y = -6, which means xy = (-5)(-6) = 30. So,
xy > 10
Since we cannot answer the
target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
