FIFO Page Replacement
A FIFO replacement algorithm associates with each page the time when that page was brought into memory.When a page must be replaced, the oldest page is chosen.
Optimal Page Replacement
Replace the page that will not be used for the longest period of time.
LRU Page Replacement
When a page must be replaced, LRU chooses the page that has not been used for the longest period of time.



 

In this example OPT algorithm is the best method. FIFO algorithm is better than LRU algorithm.