For high school mathematics teachers, the National Council of Teachers of Mathematics offers this collection of activities to help young mathematicians develop their quantitative reasoning skills. These activities have been developed by high school and college mathematics educators and can be downloaded in PDF format from this online library. Each PDF features a detailed teacher's guide as well as a student hand out. In one activity, "Cash or Gas?" students consider whether it is better to receive $250,000 in cash in an imagined lottery or free gas for life. Another activity, "As the Crow Flies," is designed to help students understand the logic and reasoning behind the Pythagorean theorem. These activities can be implemented alongside existing mathematics curriculum as they align with Common Core Standards.