Use proportions to solve this problem:
Lisa ran 3 miles in 21 minutes. At that rate, how long would it take Lisa to run 5 miles?
3/21 = 5/x?
Cross multiply and solve for x.
To solve this problem using proportions, we can set up a ratio of the distance to time for Lisa's initial run and use it to find the time it would take for her to run 5 miles.
First, let's set up the proportion using Lisa's initial run:
3 miles / 21 minutes = 5 miles / x minutes
Here, x represents the time it would take for Lisa to run 5 miles.
To solve the proportion, we can cross-multiply:
3 miles * x minutes = 5 miles * 21 minutes
Next, we divide both sides by 3 miles to isolate x:
x minutes = (5 miles * 21 minutes) / 3 miles
Now, we can simplify the equation:
x minutes = 105 minutes / 3
x minutes ≈ 35 minutes
Therefore, at the same running rate, it would take Lisa approximately 35 minutes to run 5 miles.