Question

HELP!
Jasmine is running laps on the track. It takes approximately 2 minutes and 15 seconds to complete each lap. If her friend walks up to the fence to watch her run, what is the probability that her friend will wait at least 30 seconds before Jasmine passes her?

Answer 1

Interesting question. It doesn't say where Jasmine is on the track when her friend comes up, so I guess we're supposed to assume that's "random"; that's where the probability comes in.
Basically, you could imagine the distance on the track that is within 30 seconds of where Jasmine's friend is standing. The question is asking what the probability is that Jasmine is anywhere other than within that region.

In other words, what is the probability that Jasmine is anywhere *other* than within that 30-second space?

Answer 2

Well, Jasmine could be anywhere on the track, and the whole track takes up a "space" of 2 minutes and 15 seconds or 2.25 minutes.
The 30-second region (or 0.5 minutes) makes up 0.5/2.25 of the track. So the probability that Jasmine is not in that region is equal to (1 - (0.5/2.25))