Tuesday, March 03, 2020

Teaching fractions and dealing with common misconceptions

When we move from the study of the base ten numeral system and decimals to the study of fractions and negative numbers, students mix up the decimal point and zero. Why do they do that?

When we teach place value, the decimal point lies in the center with whole numbers to the left and decimals to the right:



That matches the way we write numbers. For example we write $1.25 with the whole number to the left and the decimal number to the right.

Yet, when we move to the study of fractions and negative numbers, we often use a number line. Number lines place the zero in the center with negative numbers to the left and whole numbers to the right:

Since the zero and the decimal point sit in the same position in both models and both decimals and zeros are circles, students begin to mix up the meaning and purpose of the two.

How do we demonstrate the difference and show students that decimals and fractions are actually positive numbers equal to greater than zero. Today I'll work to dispel the misconceptions as we enter our unit on fractions. I'll use the model below. I'm curious as to how others demonstrate this difference. Let me know?