Area model for decimal multiplication

 tenths square hundredths square

A hundredths square can be used to help students understand the multiplication of decimal numbers that have one decimal place. Students must first understand what area is, and that the area of a rectangle is the length multiplied by the width. For example, consider the multiplication below.

The lengths of the sides of the whole square are each one unit. The shaded rectangle has length of 0.7 and width of 0.8. The area of the shaded rectangle is therefore 0.7 x 0.8. Looking at the shaded diagram, we can see the area of the rectangle is about half that of the square, so 0.7 x 0.8 is about 0.5. Looking more closely, the shaded area can be seen to be 56 (7 x 8) small squares i.e. 56 hundredths of the unit square are shaded.

Therefore 0.7 x 0.8 = 56 hundredths or 0.56

FOr more information, see Foundations for Teaching Arithmetic (Marston and Stacey, 2001)

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