Gil Kessler, self-described math enthusiast, always carries a four-color ballpoint pen. A former math teacher, he has found the pen to be a helpful tool in channeling his love for numbers and symbols.
“I tell the kids at the very beginning, ‘Anything we do, you can write in your notebooks in black or blue,'” he said. “‘But if it’s really interesting, use red. And if it’s unbelievably interesting, then use green.'”
Mr. Kessler taught math in New York City schools for 30 years, first at Seward Park High School on the Lower East Side, then at South Shore High School in Canarsie, Brooklyn, and finally at Canarsie High School. All the schools are now closed.
At 75, he is now retired. And when he’s not making up new math problems, playing classical piano or square dancing — one of his hobbies — he conducts math workshops for fellow teachers as part of the New York Math Circle, a non-profit organization that holds courses for both teachers and students. Most classes are held at the Courant Institute of Mathematical Sciences at New York University.