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Volume 24, Number 4
July/August 2008

When 1/2 + 1/3 = 2/5

An interview with Kay Merseth on investigating student thinking to teach fractions well


Earlier this year, the National Mathematics Advisory Panel released 45 recommendations for improving U.S. mathematics education. In particular, the report singled out proficiency with fractions as a “major goal” for K–8 math education, noting that “difficulty with fractions (including decimals and percents) is pervasive and is a major obstacle to further progress in mathematics, including algebra.” Dr. Katherine K. Merseth, director of the Teacher Education Program at the Harvard Graduate School of Education, specializes in the teaching of math and science and was inducted last year into the Massachusetts Hall of Fame for Mathematics Educators. Merseth spoke with Harvard Education Letter contributing writer Mitch Bogen about why fractions are hard to teach and what teachers can do to help students better understand this critical concept.

This is an excerpt from the Harvard Education Letter. Subscribers can click here to continue reading this article.


For Further Information

For Further Information

National Mathematics Advisory Panel. Foundations for Success: The Final Report of the National Mathematics Advisory Panel, Washington, DC: U.S. Department of Education, 2008. Available online at