Step-by-step answer:
Given:
class time uniformly distributed between 48 and 53 minutes (range 5 minutes)
Find probability that the class period runs between 51.5 and 51.75 minutes.
Solution:
Uniformly distributed means that the probability that the class time is the same for any minute (out of 5), i.e. 20%, or probability density is 0.2 / minutes, no matter which minute.
The interval between 51.5 and 51.75 is 0.25 minutes, so the probability of class period within that range is 0.25 minutes * 0.2 / minute = 0.05.