I found the following three questions from an article in the April 2006 issue of Smartmoney rather interesting:
1) A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?
2) If it takes five machines five minutes to make five widgets, how long would it take 100 machines to make 100 widgets?
3) In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half the lake?
Each question has an intuitive — but wrong — answer. See if you are ‘tricked’ by your intuition. 😉
PS. The answers are given in the Comments.