Using a time budget for a class
The numbers you reported are exceedingly common in US higher Ed. What is strange is that you reported semester totals rather than weekly totals. 

It is common in US higher ed that for every hour of class time a student will spend 2-3 hours studying and completing assignments outside of class. Therefore, if there is 45 hours of  lecture in a course there would be anywhere of 45*2=90 to 45*3 = 135 hours of individual study time for the same course.

The first example in your question requires 2 hours of study for every hour of lecture (45 lecture hours + (45 * 2 individual study)  = 135 total hours). The second example requires 180 hours of total time (45 lecture hours + (45 * 3 individual study)  = 180 total)