Of the 230 single-family homes built in City X last year, ho

we need to find how many of the 230 Built last year, were occupied at the end of last year.

1)Doesn't tell us of the 230 built last year, how many were occupied at the end.Just tells us that of all the homes present , those built last year and also those before last year, 90% were occupied at the end.

Even if we knew total number of single homes built in all years we wouldn't be able to separate how many of the newly built 230 were occupied and how many otherwise . So Insufficient.

2)Again we don't know out of the 7200 occupied , how many of the 230 were occupied , could be all 230 of the new ones are occupied or may be none. Insufficient

1+2

we would be able to find the total homes built in all years and how many of them were occupied at the end of last year, but we still wouldn't know how many of those occupied were of the 230 built last year .
Insufficient
Answer E

( Coincidentally at the end of this year (2013), got this question about end of last year )

Hi All,

We're told that 230 single-family homes that were BUILT in City X last year. We're asked for the number (of those 230) that were occupied at the end of the year. This question can be approached in a number of different ways. It's more of a 'logic problem' though, so you can beat it with some basic notes and TESTing VALUES (as needed).

1) Of all single-family homes in City X, 90 percent were occupied at the end of last year.

From the prompt, we don't know how many single-family homes existed BEFORE the 230 additional single-family homes were built. Thus, we have no way to determine what the TOTAL number of single-family homes was - nor what 90% of that number would be - nor how many of the 230 new single-family homes were occupied.
Fact 1 is INSUFFICIENT

2) A total of 7,200 single-family homes in City X were occupied at the end of last year.

Fact 2 gives us an 'absolute' number of single-family homes that were occupied, but we have no way of knowing how many of the 230 single-family homes that were built last year are included in that 7200.
Fact 2 is INSUFFICIENT

Combined, we know...
-Of all single-family homes in City X, 90 percent were occupied at the end of last year.
-A total of 7,200 single-family homes in City X were occupied at the end of last year.

With these two pieces of information, we can determine the TOTAL number of single-family homes in the city. (.9)(X) = 7200 --> X = 8000. This total includes the 230 additional homes that were built. However, we still have no idea how many of THOSE homes were occupied, so the answer to the question could be anything from 0 to 230.
Combined, INSUFFICIENT

Final Answer:

GMAT assassins aren't born, they're made,
Rich

Answer: Option E

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Solution:

Question Stem Analysis:

We need to determine the number of the 230 single-family homes built in City X last year that were occupied at the end of the year.

Statement One Alone:

Even though we know 90% of all single-family homes were occupied at the end of last year, we don’t know the number of the 230 newly-built single-family homes that were occupied at the end of the year. It’s possible that all 230 were occupied, none of them were occupied, or some of them were occupied. Statement one alone is not sufficient.

Statement Two Alone:

Even though we know 7,200 single-family homes were occupied at the end of last year, we don’t know the number of the 230 newly-built single-family homes that were occupied at the end of the year. It’s possible that all 230 were occupied, none of them were occupied, or some of them were occupied. Statement two alone is not sufficient.

Statements One and Two Together:

From the two statements, we can determine there were a total of 7,200/0.9 = 8,000 single-family homes in City X last year. However, we still can’t determine the number of the 230 newly-built single-family homes that were occupied at the end of the year. It’s possible that all 230 were occupied, none of them werre occupied, or some of them were occupied. Both statements are not sufficient.

Answer: E

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