nayasnayas wrote:
Is n < 0 ?
a) m < n
b) -n < m
Here's another approach:
Target question: Is n < 0 ?
Statement 1: m < n
There are several values of m and n that satisfy this condition. Here are two:
Case a: m = -2 and n = -1, in which case
n < 0
Case b: m = 0 and n = 1, in which case
n > 0
Since we cannot answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: -n < m
There are several values of m and n that satisfy this condition. Here are two:
Case a: m = 2 and n = -1, in which case
n < 0
Case b: m = 2 and n = 1, in which case
n > 0
Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 1 tells us that m < n
Statement 2 tells us that -n < m
IMPORTANT: Since the inequality signs are FACING IN THE SAME DIRECTION, we can
add the inequalities to get...
m
+ (-n) < n
+ m
Now subtract m from both sides to get: -n < n
Add n to both sides to get: 0 < 2n
Divide both sides by 2 to get: 0 < n
In other words,
n is definitely not less than 0
Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer =
C
Cheers,
Brent
