>>> A building has 10 floors. At the ground floor, 7 people enter the elevator. At the second floor, 3 people get off and 2 people enter. At the fourth floor, 5 people get off and 2 people enter. At the seventh floor, 1 person gets off and 3 people enter. Finally, at the tenth floor, everyone remaining in the elevator gets off. The question is, How many people were in the elevator when it started its journey, and how many total people exited the elevator by the end of its journey?

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The number of people in the elevator at the end of the journey is the same as the number that got on at the ground floor, minus the number that got off at the tenth floor. Since 7 people got on at the ground floor, and 5 people got off at the seventh floor and 1 more got off at the tenth floor, 1 person remained at the tenth floor. Therefore, 7 - 1 = 6 people were in the elevator when it started its journey, and 5 + 3 + 2 + 1 + 2 = 13 people had exited the elevator by the end of its journey. The answer is (A)