Bunuel wrote:
The average (arithmetic mean) age of the buildings on a certain city block is greater than 40 years old. If four of the buildings were built two years ago and none of the buildings are more than 80 years old, which of the following could be the number of buildings on the block?
I. 8
II. 11
III. 40
A. I only
B. II only
C. III only
D. I and II only
E. I, II and III
To check if the average age of the blocks >40 Yes/No
I
4*2 + 4*80= 328, avg >40
II
4*2 + 7*80 = 568, avg > 40
III
4*2
...
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