Numerous brain teasers along with their answers are available on the Rosetta Stone Fit Brains Blog. BrainBashers and the Woodlands Junior School website are two other online sources of brain teasers and their answers.
The answers to the brain teasers on the Rosetta Stone Fit Brains Blog are hidden until the site visitor clicks on the Reveal Answer! button, which gives the reader a chance to try to solve the problems first. An example of a brain teaser is, "A milkman has a 3-gallon milk jug and a 5-gallon jug. What does he need to do to measure precisely 1 gallon of milk without wasting any?" The answer is that the milkman must first fill the 3-gallon jug, then empty all of the milk into the 5-gallon jug. Then, he must repeat the process and stop filling the 5-gallon jug once it is full. There is then 1 gallon of milk left in the smaller jug.
A brain teaser on the Woodlands Junior School website challenges the reader to figure out how a girl can turn 10 next year if she was 7 years old the day before yesterday. The solution is that this scenario is possible if today is the first day of January. The previous day, which was Dec. 31 of last year, was the girl's eighth birthday. Thus, she was still 7 years old the previous day, and she turns 9 on Dec. 31 of the current year.