Bunuel wrote:
The Official Guide for GMAT® Review, 13th Edition - Quantitative Questions ProjectAttachment:
Triangle.png
What is the value of z in the triangle above?
(1) x + y = 139
(2) y + z = 108
Target question: What is the value of z in the triangle above?IMPORTANT: Since angles in a triangle must add to 180 degrees, we can write:
x + y + z = 180 Statement 1: x + y = 139 Take:
x + y + z = 180 and replace (x + y) with 139 to get: 139 + z = 180
Solve equation for z to get: z = 41
So, the answer to the target question is
z = 41Since we can answer the
target question with certainty, statement 1 is SUFFICIENT
Statement 2: y + z = 108 Take:
x + y + z = 180 and replace (y + z) with 108 to get: x + 108 = 180
Solve equation for x to get: x = 72
Hmmm, we know the value of x, but we have no way to find the value of z.
So, statement 2 is NOT SUFFICIENT
If you're not convinced, consider the following scenarios that satisfy statement 2:
Case a: x = 72, y = 50 and z = 58. In this case, the answer to the target question is
z = 58Case b: x = 72, y = 60 and z = 48. In this case, the answer to the target question is
z = 48Since we cannot answer the
target question with certainty, statement 2 is NOT SUFFICIENT
Answer: A
Cheers,
Brent
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