EDITED--thanks for later contributions. I see where the mistake was: we aren't losing two inches on each overlapped ruler, but rather one. Same goes for the ruler at the very end. The first ruler, however, we count as 12 inches.
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X______________
X_____________ etc.
To explain: we count 12 inches for the very first ruler, and 11 inches for all subsequent rulers. Another way to think about it is that we've clipped an inch of the front of each one EXCEPT the first, which doesn't get the clip.
For 99 clipped rulers, that is 99*11 = (100-1)11 = 1089 inches. Now we add the 12 inches for the first, unclipped ruler: 1089 + 12 =
1101 inches. The next question is how many feet this gives us, so we must divide by 12.
Obviously 1200 is 12*100 and we know that 12*9 = 108. Therefore the closest multiple of 12 is 1200-108 = 1092. How many feet is this?
1200 - 108 = 12*100 - 12*9 = 12 (100-9) = 12*91 =
91 feet, with a remainder of 9 inches to reach 1101 inches.
Answer D.**This definitely assumes knowledge that 12 inches = 1 foot. Ideally the test will tell you, but it's a good one to memorize if you're smart and use metric.
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