Question

Shelly biked 21 miles in 4 hours. What is shellys average speed in miles per hour? At the same rate how many hours will it take Shelly to bike 42 miles?

Answer 1

Answer:  The average speed of Shelly is 5.25 miles per hour and she takes 8 hours to bike 42 miles.

Step-by-step explanation:  Given that Shelly biked 21 miles in 4 hours.

We are to find the average speed of Shelly in miles per hour. Also, to find the number of hours that Shelly take to bike 42 miles.

We will be using the UNITARY method to solve the problem.

Number of miles biked by Shelly in 4 hours = 21 miles.

So, number of miles biked by Shelly in 1 hour will be

$\dfrac{21}{4}=5.25~\textup{miles}.$

Now, number of hours Shelly take to bike 5.25 miles = 1 hour.

So, number of hours Shelly take to bike 1 mile will be

$\dfrac{1}{5.25}~\textup{hours}.$

Therefore, number of hours Shelly take to bike 42 miles is given by

$\dfrac{1}{5.25}\times42=8~\textup{hours}.$

Thus, the average speed of Shelly is 5.25 miles per hour and she takes 8 hours to bike 42 miles.

Answer 2

21 divide by 4 is 5.25. She travels 5.25 miles per hour.  42 divide by 5.25 is 8. It would take 8 hours for Shelly to bike 42 miles.