Just because you are a math wizard doesn't mean you perform well under pressure. That's why Jeremy Kahn, US math prodigy, was so happy to win a gold medal this week in the International Mathematical Olympiad (IMO) in Helsinki. When the mathematical dust finally settled this past Monday, the Romanians emerged as the solid team winner in this year's IMO. The six-member US team, led by Kahn of New York and Waldemar Horwat of Illinois, took second place in the two-day competition among the best pre-college math students from 30 countries. (Among others, the United States came in ahead of Hungary, Bulgaria, Vietnam, and the Soviet Union, which placed an unexpectedly poor sixth.)

This was Kahn's third IMO, although he is only a high school sophomore. According to his close friend John Overdeck, whom Kahn telephoned from Helsinki, Kahn was ``very pleased,'' since he had not done as well in recent key tests.

In fact, the evening before he left for Finland, Kahn was presented with a problem he couldn't solve.

He was seated at a table here in the huge West Point dining hall -- faced with the task of cutting a large apple pie into nine equal pieces for his fellow math-team members and coaches about to depart for Helsinki.

``I can't do it,'' he moaned humorously. To make nine equal cuts, he was ``forced to come up with a construction to trisect the angle -- and that's impossible!''

Pie aside, young Kahn has been solving ``impossible'' math problems for years. Today, at age 16, his math r'esum'e is formidable: At age 7, his parents gave him Isaac Asimov's ``The Realm of Algebra,'' and Kahn mastered quadratic equations. At 8, his math teacher gave the class an extra-credit problem which Kahn not only solved, but designed an equation for solving. A little checking by teachers found that the equation was identical to one Karl Gauss, the famous German mathematician and astronomer, formulated in 1786 at the age of 9. At 10, Kahn proved the Pythagorean Theorem. At 11, he scored a phenomenal 780 out of a possible 800 on the college SAT math test. And on and on.

Dr. Julian Stanley of Johns Hopkins University, who runs a summer school for gifted students that Kahn helps teach, says the young man is one of the most ``mathematically precocious individuals the country has ever had.''

Neither of Kahn's parents is especially mathematical. And initially Jeremy's mother, Carol, was concerned about his precociousness. She remembers driving a mop-headed 12-year-old Jeremy down to Annapolis, Md., from their home in New York City to study for his first international competition, seeing the high school students twice his size, and thinking, ``He's a little boy. Why can't he just do little-boy things?''

Mrs. Kahn says, however, that Jeremy has adjusted well to life at his pace.

Kahn is both serious and playful. He enjoys a good game of ultimate Frisbee as much as any of his contemp oraries. But what he finds surprising is that other high school students should find math a dull subject.

In fact, he doesn't think they really find it dull. Just incomprehensible. And he says this is because of misperceptions brought about by the way mathematics is taught.

Kahn feels math teaching needs to be upgraded at all levels -- especially high school. He puts in a bid for math teachers to ``find new ways of introducing the subject.''

``The concepts behind mathematics are fascinating,'' he says, ``but most high school math is a process of symbolic manipulation -- a computer could do it.''

``Math isn't going to be stimulating if all you are doing is plugging in numbers by rote,'' he says. Teachers need to get at ``what's behind the symbols.''

Dr. Stanley feels Kahn's ideas are especially true for more-talented students. But he also notes that the so-called ``modern math,'' introduced after the launching of Sputnik, may be too theoretical an approach for students simply uninterested in the subject. ``Too much abstractness would freeze them out,'' he says.

What a student like Jeremy Kahn does highlight, says Stanley, is the need for more thoughtful ways to encourage gifted students, ``more curricular flexibility'' in the schools -- ``a way to take algebra a year early if necessary.''

Thus far in American education, Stanley says, ways to accommodate gifted students have been lacking. He has seen too many examples of talent wasted by students ``bored and turned off'' by a pace too slow for them. That needs to change, he says.

Fortunately, Kahn lives in New York, so he can attend a special program for young, gifted students run by Hunter College. Mrs. Kahn says finding the program was ``a turning point'' for Jeremy, a chance for him to meet peers who share his interests.

Jeremy's peers say it is hard to say exactly what he will do next. Overdeck, who just missed the IMO cutoff this year, says, ``His interest is in everything -- he does anything that comes around.'' Kahn, his friend sums up, ``loves math for math's sake. He finds math rather beautiful.''

Second of two articles on the IMO. The first article ran July 5 on Page 1. A sample question from math Olympics Here's one of the problems given to the pre-college teams from 30 countries at the 1985 International Mathematical Olympiad in Helsinki: ``Given a set M of 1,985 distinct positive integers, none of which has a prime divisor greater than 26, prove that M contains at least 1 subset of 4 distinct elements whose product is the 4th power of an integer.'' m30{et