Math Challenge. Use this MINI Project Based Learning (PBL) in your classroom to have your students incorporate critical thinking, and real-life Earth Day math in a fun way (Percentages, Fractions, Decimals). Printable & Digital (EDITABLE).*You can use it as a fractions & decimals activity. Percent calculations may be optional.You must help save the Earth and score as many points as possible. Calculate your number of points according to the selected activities, approximate area, and populati