What is the average (arithmetic mean) of A, B, and 4C?

Question

(1) A + B = 17

(2) C^2 = 49

Bunuel · Answer

Straight E.

When combined C is either 7 or -7, which give two answers for (A + B + 4C)/3.

Answer: E.

prateekbhatt · Answer

But cant we put the value of A+B =17 as given in option 1.

(A+B+4C)/3=?

(17+4C)/3

4C= 3-17

C= 14/4

C= 7/2

Cant we do it this way?

Bunuel · Answer

You can notice that C cannot be 7/2 from the fact that  on the GMAT, two data sufficiency statements always provide TRUE information and these statements never contradict each other . From (2) we have that C is 7 or -7, and if from (1) you get that C is 7/2 it would mean that the statements clearly contradict.

As for your solution. For (1) we need to find the value of (17+4C)/3. How you do get 4C= 3-17?

stonecold · Answer

Nice Question.
Here is what i did in this one=>

We need the sum => a+b+4c to get the average -> a+b+4c/3

Statement 1->
No clue of c
Not sufficient

Statement 2->
c=7 or -7
No clue of a or b
Not sufficient

Combing them => a+b+4c=> 17+28 or 17-28

Hence not sufficient

Hence E

What is the average (arithmetic mean) of A, B, and 4C?

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GMAT Data Sufficiency (DS) Questions

What is the average (arithmetic mean) of A, B, and 4C?

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