Bunuel wrote:

A marathoner ran for two days. On the second day he ran at an average speed of 3 mile 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 was 36/8 = 4.5 mph

Thus, since the speed on the first day was 3 mph slower than that of the second day, the speed on the first day must be less than 4.5 mph and the speed on the second day must be greater than 4.5 mph.

Since the speed on the second day is greater than 4.5 mph, which is 3 mph faster than that of the first day, the speed on the first day must be greater than 1.5 mph. So the only possible speed on the first day, from the given answer choices, is 2 mph.

Answer: E

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