In Math, Magic, Games & Puzzles, longtime Northeastern mathematics professor Stanley Eigen uncovers the numerical principles behind popular card tricks — and helps his honors students teach them to kids.

Walking in to an honors-level math seminar on Northeastern University’s Boston campus in early September, you might expect to see graphing calculators, thick textbooks, algebraic equations and parabolas scratched on a marker-board — trappings of the serious work that the best STEM-focused students at a world-class research university are undertaking.

Instead, in Stanley Eigen’s class, you’ll see a flurry of shuffling playing cards; hear a dim cacophony of awed chatter. You’ll watch a grainy YouTube video of the ’90s-era celebrity magician David Copperfield, who, in between corny jokes and a terrible moonwalk, correctly identifies the seemingly random card that you, the home viewer, have pulled from your deck.

This is HONR 1310: Math, Magic, Games & Puzzles, for freshmen in Northeastern’s honors program. It covers the mathematical concepts underlying well-known card tricks and puzzles, but the more important takeaway is how to communicate them effectively. This is a service-learning course, and students must perfect the tricks in order to teach them to elementary- and middle-school-age kids in Boston-area partner programs.

Today’s lesson, just the second of the semester, is devoted to card tricks that use “orbits” — predictable paths of a numerical system. Eigen starts with the “Nine Card Liar” trick. (You, readers, can now grab a deck and play along).