In the fourth installment of this illustrated problem set, students use the mathematical constant pi to solve real-world science and engineering problems. Students will use pi to calculate the angle of crater impacts on Mars, measure the size of the shadow that will fall on North America during the 2017 total solar eclipse, determine the orbital period of the Cassini spacecraft during its final weeks around Saturn, and find the habitable zone around TRAPPIST-1, a star that is home to seven Eart