A certain bridge is 4,224 feet long. What constant rate, in miles per hour, must be maintained in order to walk across the bridge in 12 minutes? (1 mile = 5,280 feet)

4miles/hour

Explanation:

the solution for this question requires that the quantities are converted to the appropriate units as required by the question.

Rate in miles per hour = distance in miles / time in hour

to convert 12 minutes to hours; recall that 60 minutes make 1 hour

12 minutes to hour = 12/60 = 0.2hr

to convert 4224 feet to miles; recall 5280 feet is equivalent to 1 mile

4224 feet to miles = 4224/5280 = 0.8 miles

∴ rate = 0.8 / 0.2

rate = 4 miles per hour

the constant rate in miles per hour = 4 miles/hour