Question

Alex can run 21 1/2 miles in 2 1/4 hours. How many miles can she run per hour?

Answer 1

86/9 mph or 9.5555556 mph

Explanation:

This is a bit of unit math. If we're looking at a speed of 'miles per hour', we can re-write it as `"miles"/"hour"` since its the number of miles covered every hour.

We know that Alex can run 21 1/2 miles in 2 1/4 hours, that means that the speed can be determined as:

`((21 1/2)"miles")/((2 1/4)"hours")`

Let's raise everything to the same denominator:

21 1/2 miles = 43/2 miles = 86/4 miles
2 1/4 hours = 9/4 hours

and re-write that fraction:

`((86/4)/(9/4))`

Now we can remove the denominators from the top and bottom, and get our solution:

`color(red)(86/9 mph = 9.55555556mph`