January 10, 1992|By Lan Nguyen | Lan Nguyen,Evening Sun Staff

THE AUDIENCE came with calculators in hand, ready to trip up Arthur Benjamin -- the human calculator, the walking computer -- the mathematician who can figure out math problems faster than the best-made machines.

The audience -- composed of learned math professors and students, no less -- lost, and so did the machines. Benjamin figured out the square of 675 faster than they could say arithmetic. He reeled off the answer to "3,969 x 1,225" faster than they could tie their shoelaces.

He calls it the art of mental calculation, a process that can be learned, practiced and perfected. "It's not something you are born with," he said. "If I was born with anything, it was with genuine mathematical interest, a natural fascination."

Benjamin performed yesterday at the Convention Center for a standing-room-only audience of about 700 people who are part of this week's joint convention of the American Mathematical Society and the Mathematical Association of America.

Benjamin, 30, went to Carnegie-Mellon University for his undergraduate math degree and later attended Johns Hopkins University for his master's and Ph.D. in mathematical sciences.

In his one-hour presentation, the Harvey Mudd College math professor unveiled the tricks of the trade: memorizing long numbers, multiplying without pen and paper, figuring out square roots lickety-split.

Anybody can do it. "Of course, I'm just a little bit faster because I've been doing it half my life," he said.

But even the most hapless can follow the pattern and learn. The trick is to work with numbers that can be used with little difficulty.

To multiply two or more digits, for example, Benjamin breaks down the numbers to handle them more easily. If "61 x 27" were the problem, Benjamin would break 61 into 60 and 1, then multiply 27 by 60 (which equals 1,620) and 27 with 1 (which amounts to 27). Then he adds 1,620 to 27, getting the grand answer of 1,647.

It doesn't take a miracle to grasp mathematics. "I think for most people, it's simply a matter of wanting enough," he said. "Learning to read is very difficult. Most people struggle to learn it. But when they get it, it's with them forever. It's the same for mathematics, but not many people are willing to take the time to conquer it."

Benjamin's mother is a teacher, and his father's an accountant. His spare moments in youth were spent thinking about patterns and numbers. As he stood in line or rode the bus, he would devise mathematical configurations and shortcuts. "When I was young, I did small problems," he said. "When I grew older, I did larger problems."

He says he's got zillions of patterns and quickies, some of which will be published in his new book, "Mathemagics: The Art of Mental Calculation," due out later this year. His book teaches people to calculate numbers and problems quickly and easily. And then there are chapters devoted to teaching people how to impress and show off to friends as well as how to look like a genius without really trying.

"I love numbers and patterns," he said. "It's the fact that you can take a problem and do that problem in different ways and still come up with the same answer. I find that fascinating."