Change the factors with the sliders:
H, T, and O are the hundreds, tens, and ones digits for the first (horizontal) factor; h, t, and o are for the second (vertical) factor.
You will need to zoom out to see products larger than 100 x 40. (Last button on right, thrid button down.) Click at (0,0), where the x and y axes meet, for best results. See NavigatingGeogebra.pdf for a quick guide, or the GeoGebra website for more detailed instructions.
In the U.S., paper-and-pencil multiplication is taught with a method that starts with ones times ones. This diagram shows that ones times ones is a tiny part of the product. Could you invent a multiplication method that starts with the highest place values?
Can you adapt this diagram/method to multiply decimals? Maybe think of the numbers on the axes as counting hundredths instead of ones (for example, 37 might mean 37 hundredths, or 0.37.)
Susan Addington, Created with GeoGebra |
