An unmarked straight stick will be laid end over end to measure a distance of exactly 72 feet. The same stick will be used in the same way to measure a distance of exactly 30 feet. What is the length of the longest possible stick that can be used for both measurements?
- A3 ft
- B4 ft
- C6 ft
- D8 ft
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Correct answer: C
The length of the stick must be the greatest common factor of 72 and 30.
The factors of 30 are
1, 2, 3, 5, 6, 10, 15, and 30.
Of those, only 1, 2, 3, and 6 are also factors of 72. The greatest of these is 6.