Before coming to the United States, Chang said, he was an instructor in math at a university in his native China. After winning a fellowship to attend Penn State University, Chang came to America, where he earned his Ph.D. in math.

Every two weeks this spring, Chang has provided a math question to Diane Cree, student achievement specialist at the school. The students who want to participate are given copies of the problem and then they try to solve it.

"The younger students can use the trial-and-error method while the older students use algebra," Cree said. In either case, students have to show their work.

Chang said another benefit of the math award program is that it teaches children honesty since it is imperative they do their own work.

Emily Winters, a sixth-grader, said she had little trouble with the second math question Chang posed for the students.

The question was: Five people ate lunch at Windy Hill restaurant. The total cost was $33. Maryland sales tax is 5 percent of the total and the group left a 15 percent tip based on the cost of the total meal. They have one $4.50 coupon. How much does each person need to pay?

Emily, 12, did the math: "My answer was $7.02," she said.

Brandon Stride, 11, also worked out the problem but got $7.07, he said.

Both answers were ruled correct since the students showed their methods for reaching the answer, and each student got a gift certificate.

The prize for solving the current math problem is a $4.50 gift certificate to Windy Hill. Cree said Chang has agreed to also reward with gift certificates any students who at least try to solve all four of the math problems.

The first time, there were six winners out of 13 students who tried the problem. The second question had 20 winners out of 36 entries, Cree said.

"I see boys and girls doing physical education but they might need to exercise their brains, too, in a fun way," Chang said.

He said he also sees the program as leading students to pursue knowledge and as a way to build good character at an early age.

"The 21st century belongs to our students," Chang said during a recent visit to the school. "I want to do good for people."