Dr. Andreescu has allowed me to post some of the problems from his AMC 8 preparation sessions. Students are welcome to give their answers in the comments section. Even better would be to use the comments section to defend or extend your answer.
One half of the water is poured out of a full container. Then one third of the remainder is poured out. Continue this process: one fourth of the remainder for the third pouring, one fifth of the remainder for the fourth pouring, etc. After how many pourings does exactly one tenth of the original water remain?
A) 6 B) 7 C) 8 D) 9 E) 10
Students interested in more problems like this one should attend our upcoming session. I’ll post a couple more problems to the site this week as well.
Metroplex Math Circle 
Answer: (E) 10