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Introducing the decimal point

In 1981, Margaret Brown found that approximately half of a sample of 12-year-old children and a third of 15-year-olds did not understand decimal notation. It appeared that many students seemed to think that the figures after the decimal point represented a different number that also had tens and units.

Rather than helping students understand decimals, money might actually add to the confusion. When we read $3.52 as “three dollars, fifty two” the figures after the decimal point are more readily interpreted as a whole number of cents than as a fraction of a dollar. Developing a complete understanding of decimals requires both understanding and using the notational conventions of the place value system of recording, as well as grasping the underlying fraction concept of, say seven-tenths, and the structure of composite units.