Esti-Mysteries are developed by Steve Wyborney and help students to develop their math reasoning, vocabulary, and number sense skills. Each of the Esti-Mysteries starts with a single image and students make an estimate of the number of objects in a container. Then, one at a time, clues are given to help students refine their estimate. The clues include math vocabulary and skills (greater than, less than, even/odd, prime, etc.) to help students narrow down the possible options for the total number of objects. Plus, the Esti-Mysteries are leveled, so you can find a mystery that matches your students’ grade-level. At the end of the activity, the mystery is solved and the answer is revealed!