Final answer:
Robbie consistently runs at a speed of 2 miles per hour, as shown by running 2 miles in an hour each day. Thus, on the fifth day, Robbie will continue to run at 2 mph regardless of the distance covered.
Step-by-step explanation:
From the provided problem, we can see that Robbie consistently runs at a pace of 2 miles per hour (mph) each day. On the first day, Robbie ran 2 miles in 1 hour. On the second day, he ran 4 miles in 2 hours, and on the third day, he ran 6 miles in 3 hours. Each of these events shows he maintains a speed of 2 miles per hour, as the miles run each day are directly proportional to the hours spent running. Therefore, no matter how many miles Robbie runs on the fifth day, he will be running at a speed of 2 mph.
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