Answer:
C. 400 miles
Explanation:
In each hour, it travels 80 miles. (That is the meaning of "80 miles per hour.") So you can add up the distances over a period of 5 hours:
80 miles + 80 miles + 80 miles + 80 miles + 80 miles
After the first sum (80+80=160), you can see what the correct answer will be. Continuing, you find the sum to be ...
= 400 miles
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Multiplication was invented to make repeated addition easier.
5 × 80 miles = 400 miles
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Strictly speaking, you are multiplying numbers with units here:
(5 h) × (80 mi/h) = 400 mi·h/h = 400 mi . . . . . . the units h/h cancel