It takes 25 minutes to ride a bike 3.5 miles. What is my speed in miles per hour ?

Question

Trying to help.my son with his math problem. It takes Marcus 25 minutes to ride his bike 3.5 miles

 What is his speed in miles per hour?

Answer 1

First we have to change the measurements:

 

25 minutes = 25/60 hr = 5/12 hr

 

3.5 miles  = 3 and 1/2 miles = 7/2 miles

 

Next we have:

Distance = rate x time, so rate = distance / time

 

Then

 

7/2 miles divided by 5/12 hr = 

 

7/2 miles x 12/5 hr <------ remember when dividing fractions, KFC: keep , flip, change

 

84/10 miles per hour

 

So 8 and 4/10 miles per hour = 8 and 4/10 mph

    8 and 2/5 miles per hour = 8 and 2/5 mph

    8.4 miles per hour = 8.4 mph

 

are several ways to write the same answer.

Happy New Year

Answer 2

Speed in miles per hour.

   Miles / hour

  3.5 miles / 25 minutes

  3.5 miles / (5/12 hour)

  (3,5)(12/5)  miles/hour       [to divide by fraction, invert denominator and multiply]

   8.4 miles/hour