Bunuel wrote:

If a + b + c = 12, what is the value of b ?

(1) a + b = 8

(2) b + c = 6

Target question: What is the value of b ? Given: a + b + c = 12 Statement 1: a + b = 8 We can take

a + b + c = 12 and rewrite it as

(a + b) + c = 12Now replace a+b with 8 to get: (8) + c = 12

Solve: c = 4

Now that we know the value of c, can we find the

value of b?

No.

Let's TEST some values that satisfy statement 1. Here are two:

Case a: a = 1, b = 7 and c = 4. In this case, the answer to the target question is

b = 7Case b: a = 0, b = 8 and c = 4. In this case, the answer to the target question is

b = 8Since we cannot answer the

target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: b + c = 6 We can take

a + b + c = 12 and replace b+c with 6 to get: a + 6 = 12

Solve: a = 6

Now that we know the value of a, can we find the

value of b?

No.

Let's TEST some values that satisfy statement 2:

Case a: a = 6, b = 5 and c = 1. In this case, the answer to the target question is

b = 5Case b: a = 6, b = 4 and c = 2. In this case, the answer to the target question is

b = 4Since we cannot answer the

target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined Statement 1 tells us that c = 4

Statement 2 tells us that a = 6

We can take

a + b + c = 12 and replace c and a with 4 and 6 to get: 4 + b + 6 = 12

Solve:

b = 2Since we can answer the

target question with certainty, the combined statements are SUFFICIENT

Answer: C

Cheers,

Brent

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Brent Hanneson – GMATPrepNow.com

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