A runner takes 20 seconds to run 100 meters. How long to run 25 meters?

(Ex. 25/100 = 20/?)

You've misstated the ratio.

20/100 = x/25

Cross multiply and solve for x

100x = 500
x = 500/100
x = 5

oh thank you!!

You're welcome.

To find out how long it would take to run 25 meters, we can set up a proportion using the given information.

Let's set up the proportion:
25/100 = x/20

To solve for x (the time it would take to run 25 meters), we can cross-multiply and solve for x:

25 * 20 = 100 * x
500 = 100x

Next, divide both sides by 100 to solve for x:

500/100 = x
5 = x

Therefore, it would take 5 seconds to run 25 meters.