Bunuel wrote:

The Official Guide For GMAT® Quantitative Review, 2ND EditionOf the 230 single-family homes built in City X last year, how many were occupied at the end of the year?

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

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

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 )

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- Stne