Colin drove 45 minutes to the airport. He arrived 90 minutes before his flight departed, and then he spent 70 minutes in the air. Once he landed, Colin spent 20 minutes gathering his luggage, and then he drove 35 minutes to his hotel. What must be true of any expression that represents the total time that Colin spent traveling from his house to the hotel?
Answer
A
The numbers can be added in any order.
B
The number 45 must be the first addend, and 35 must be the last addend.
C
The numbers must be added in the order 45, 90, 70, 20, and 35.
D
The numbers must be added in either the order 45, 90, 70, 20, and 35 or the order 35, 20, 70, 90, and 45.
Explanation
The total time is the sum of the five time intervals: 45 + 90 + 70 + 20 + 35 minutes. Addition is commutative and associative, so these numbers can be rearranged and grouped in any order without changing the total. Therefore, the numbers can be added in any order.
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