University of Cambridge
University of Cambridge: Nrich: A Flying Holiday
Some may think this problem is for the birds but you will need to use your problem solving skills to come up with a reasonable answer. Then check this one page website for the solution.
University of Cambridge
University of Cambridge: Nrich: Hand Span
Use this one page website to practice measuring things using nonstandard units of measurement. There is a solutions page that is right at the website for more information.
University of Cambridge
University of Cambridge: Nrich: Dining Ducks
This problem will quack you up. On this one page website use those problem solving skills to check the reasonableness of your answer. The solution is available right at the website.
University of Cambridge
University of Cambridge: Nrich: A Rod and a Pole
At this one page website work on this challenge using your very best problem solving skills to find a reasonable answer. Actually, there are a number of solutions. When you find yours check the website to see the solutions already listed.
Education Place
Houghton Mifflin: Eduplace: Justifying Answers
Justifying answers, easy enough to an adult, can be difficult for a child. This is a great place to help you teach the concept of "reasonableness" of an answer. There are sections covering lesson plans, tips & tricks, and...