NandishSS wrote:Bill spends two days driving from Point A to Point B . On the first day, he drove 2 hours longer and at an average speed 5 miles per hour faster than he drove on the second day. If during the two days he drove a total of 680 miles over the course of 18 hours, what was his average speed on the second day, in miles per hour?
A) 20
B) 25
C) 28
D) 30
E) 35
Since the total time = 18 hours, and the time on the first day is 2 hours longer than the time on the second day, the first day = 10 hours and the second day = 8 hours.
An alternate approach is to PLUG IN THE ANSWERS, which represent the speed on the second day.
When the correct answer choice is plugged in, the total distance traveled = 680 miles.
Answer choice D: 30mph per hour on the second day, implying 35mph on the first day
Since the speed on the first day = 35mph, and the time on the first day = 10 hours, the distance on the first day = rt = 35*10 = 350 miles.
Since the speed on the second day = 30mph, and the time on the second day = 8 hours, the distance on the second day = rt = 30*8 = 240 miles.
Total distance = 350+240 = 590 miles.
The total distance is TOO SMALL.
Since the total distance must INCREASE, the two speeds must also increase.
The correct answer is
E.
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