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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