Astatistics professor plans classes so carefully that the lengths of her classes are uniformly distributed between 45.0 and 55.0 minutes. find the probability that a given class period runs between 51.5 and 51.75 minutes.
find the probability of selecting a class that runs between 51.5 and 51.75 minutes.

Given:

Uniform distribution of length of classes between 45.0 to 55.0 minutes. 

To determine the probability of selecting a class that runs between 51.5 to 51.75 minutes, find the median of the given upper and lower limit first:

45+55/2 = 50

So the highest number of instances is 50-minute class. If the probability of 50 is 0.5, then the probability of length of class between 51.5 to 51.75 minutes is near 0.5, approximately 0.45.