Question

The time, t, it takes a runner to cover a specified distance is inversely proportional to the runner's speed. If Jann Avery runs at an average of 6 miles per hour, she
will finish a race in 2. 1 hours. How long will it take Jackie Donofrio, who runs at 4 miles per hour to finish the same race?

Answer 1

To solve this problem you will need this tool, it is the formula of speed :

speed = distance/time

(I suggest you to remember this one for life, it is a really useful one)

Let's check how long that Jackie nice dude will take to finish the race...

Jann avery runs at an average of 6 mph (miles per hour), so we already got the speed for our formula. And she will finish the race in 2.1 hours so we got the time. What do we miss ? The distance.

Let's write what we already know to solve this puzzle :

6 = d / 2.1

Where d is that unknown distance..  So we are in front of an equation here let's solve it :

d / 2.1 = 6

d = 6 * 2.1

d = 12.6 miles

Now that we know that distance, for the race, we can see if that poor Jackie Donofrio has all his chances to catch Jann Avery...

We already know his speed... and since we have the distance, we write :

4 = 12.6 / t

Where t is the unknown time, for Jackie, to finish the same race. Let's solve the equation :

4t = 12.6 (we multiplied t on each side of the equation)

t = 12.6 / 4

t = 3.15

Jackie Donofrio, who runs at 4 miles per hour, will finish the race in 3.15 hours

Good Luck