Bunuel
Is y < 40?
(1) y - x > 40
(2) x + y = 40
Target question: Is y < 40? Statement 1: y - x > 40 This statement doesn't feel sufficient, so I'll TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: y = 50 and x = 1. In this case, the answer to the target question is
NO, y is NOT less than 40Case b: y = 30 and x = -20. In this case, the answer to the target question is
YES, y is less than 40Since we can’t answer the
target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: x + y = 40There are several values of x and y that satisfy statement 2. Here are two:
Case a: y = 50 and x = -10. In this case, the answer to the target question is
NO, y is NOT less than 40Case b: y = 30 and x = 10. In this case, the answer to the target question is
YES, y is less than 40Since we can’t answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined Statement 2 tells us that x + y = 40, which means
x = 40 - yStatement 1 tells us that y - x > 40
Replace
x with
40 - y to get: y - (
40 - y) > 40
Simplify: 2y - 40 > 40
Add 40 to both sides of the inequality: 2y > 80
Divide both sides by 2 to get:
y > 40So, the answer to the target question is
NO, y is NOT less than 40Since we can answer the
target question with certainty, the combined statements are SUFFICIENT
Answer: C
Cheers,
Brent