Answer:
One chance in 12,607,306.25
Explanation:
The number of ways the 5 first numbers on your lottery ticket can match the 5 White numbers is COMBIN(5,5) = 1. The number of ways your final number can match any of the 24 losing Mega numbers is: COMBIN(24,1) = 24. (Pick any of the 24 losers.) Thus there are COMBIN(5,5) x COMBIN(24,1) = 24 possible combinations.