# Sanjoy Mahajan

# Sanjoy Mahajan

Associate Professor of Applied Science and Engineering, Olin College

Sanjoy Mahajan thinks schools teach science and mathematics the wrong way round. Instead of focusing on precise calculation in the beginning, schools should teach rough-and-ready approximation first, to give students a feel for comparative quantities. "The uncompared number is not worth knowing," he says.

Sanjoy, a theoretical physicist who until recently headed the Teaching and Learning Laboratory at the Massachusetts Institute of Technology and now teaches at Olin College of Engineering, has been using this approach with students for nearly 20 years, and many former students later tell him it's the most useful thing they learned. He also describes his approach in his book, *Street-Fighting Mathematics: The Art of Educated Guessing and Opportunistic Problem-Solving*.

Searching for ways to come up with approximate answers forces students to understand the patterns and concepts behind what they learn instead of just memorizing facts. For instance, Sanjoy likes to demonstrate how he can roughly estimate the fuel efficiency of a jumbo jet by timing the fall of two conical coffee filters of different sizes. In the process, students have to make educated guesses about the relation between drag force and velocity, estimate the speed of the jet, and bring in other bits of knowledge about the world. "We can make physics and math teaching much more effective and interesting," he says.

Earlier in his career, Sanjoy served as the first curriculum director of the African Institute of Mathematical Sciences, where he designed a one-year postgraduate curriculum that stressed understanding rather than memorization and problem-solving rather than formal lectures. By 2030, he hopes that high schools, too, will stress insight rather than memorization.

Outside of work, Sanjoy likes to cook and play the piano.