We love books that make you think “ and this one surely does! Colorful photographs of everything from pennies to penguins help train the eye to make good estimates. Children (and adults) will learn what groups of 10 and 100 look like and will master tricks on how to estimate. Thought-provoking, brain-building, and laced with wonderful, subtle humor. Perfect for Montessori Elementary classrooms. 32 pages. Ages 5 and up.