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A bicycle is traveling at 21 miles per hour. How many feet will it cover in 30 seconds? Round your answer to the nearest tenth of a foot.

Sagot :

Answer:  19,404 feet

Your teacher may want you to delete the comma.

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Explanation:

Let's start with these facts

  • 1 mile = 5280 ft
  • 1 min = 60 sec
  • 60 min = 3600 sec (multiply both sides by 60)
  • 1 hour = 3600 sec

The main takeaways here are that 1 mile = 5280 ft and 1 hr = 3600 sec.

We'll use those two facts to then convert from mph to feet per second.

[tex]21 \text{ mph} = \frac{21 \text{ mi}}{1 \text{ hr}}*\frac{5280 \text{ ft}}{1 \text{ mi}}*\frac{1 \text{ hr}}{3600 \text{ sec}}\\\\\\21 \text{ mph} = 21*\frac{5280}{3600} \text{ ft per sec}\\\\\\21 \text{ mph} = 21*30.8 \text{ ft per sec}\\\\\\21 \text{ mph} = 646.8 \text{ ft per sec}\\\\\\[/tex]

This value is exact.

Since the bike is moving at exactly 646.8 ft per second, this means that after 30 seconds, the bike has traveled exactly 646.8*30 = 19,404 feet

I'm using the formula:  distance = rate*time

Side note: 19,404 feet is exactly equal to 3.675 miles (divide by 5280 to convert from feet to miles).