Data Sufficiency

If every car sold last week at a certain used-car dealership was either a coupe or a sedan, what was the average (arithmetic mean) sale price for all the cars that were sold at the dealership last week?

(1)The average sale price for the sedans that were sold at the dealership last week was $10,600.
(2)The average sale price for the coupes that were sold at the dealership last week was $8,400.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


can i devide the sum of two means by 2 to get a new mean？

OA（E）

no, you cannot divide the sum of the means by 2 to get the overall average, as we do not know the proportion/weights of the sedans and the coupes. you could do that if you knew you had equal number of sedans and coupes

seanceserene wrote:If every car sold last week at a certain used-car dealership was either a coupe or a sedan, what was the average (arithmetic mean) sale price for all the cars that were sold at the dealership last week?

(1)The average sale price for the sedans that were sold at the dealership last week was $10,600.
(2)The average sale price for the coupes that were sold at the dealership last week was $8,400.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.


can i devide the sum of two means by 2 to get a new mean？

OA（E）

The average (arithmetic mean) sale price for all the cars that were sold at the dealership last week = (number of sedans sold × $10,600 + number of coupes sold × $8,400) / (number of sedans sold + number of coupes sold)

No statement (even if taken together) gives us the number of sedans and coupes sold; wholly insufficient

[spoiler]E[/spoiler]

We can add and divide it by 2, only if we're given that number of sedans sold = number of coupes sold; hence, we can't!