calculate the effective access time

Question

This is a paragraph from Operating System Concepts, 9th edition by Silberschatz et al:

The percentage of times that the page number of interest is found i

Answer 1

The effective time here is just the average time using the relative probabilities of a hit or a miss. So if a hit happens 80% of the time and a miss happens 20% of the time then the effective time (i.e. average time) over a large number of hits/misses will be 0.8 * (hit time) + 0.2 * (miss time).