Mary has two methods to depart from A to C. The first one is A-B-C with speed of 80 meters per hour, and the other one is A-C with speed of 60 meters per hour. How many hours Mary used in A-C less than used in A-B-C?
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数学PS
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Mary has two methods to depart from A to C. The first one is A-B-C with speed of 80 meters per hour, and the other one is A-C with speed of 60 meters per hour. How many hours Mary used in A-C less than used in A-B-C?
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正确答案: E