aaron1981 wrote:A marathoner ran for two days. On the second day, he ran at an average speed of 3 miles per hour faster than he ran on the first day. If during the two days he ran a total of 36 miles and did a total of 8 hours running, which of the following could be his average speed, in miles per hour, on the first day?
(A) 0.25
(B) 0.50
(C) 1.00
(D) 1.50
(E) 2.00
The average speed for the entire two days must be BETWEEN the slower speed on the first day and the faster speed on the second day.
Average speed for the entire two days = (total distance over the two days)/(total time over the two days) = (36 miles)/(8 hours) = 9/2 = 4.5 miles per hour.
We can PLUG IN THE ANSWERS, which represent the speed on the first day.
Since the speed on the second day is 3mph faster than the speed on the first day, we get the following options:
A: 0.25 mph on the first day, 3.25 mph on the second day
B: 0.5 mph on the second day, 3.5 mph on the second day
C: 1 mph on the first day, 4 mph on the second day
D: 1.5 mph on the first day, 4.5 mph on the second day
E: 2 mph on the first day, 5 mph on the second day
Since the average speed for the entire two days -- 4.5 mph -- must between the slower speed and the faster speed, only the option in blue is viable.
The correct answer is
E.
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