You can use grids to show decimal multiplication. Let's try it with Use a grid to show a rectangle with side lengths 0.3 and 0.5. Each side of the big square is one unit long.
The of the shaded rectangle is the product There are 100 small squares on the grid. So, each small square has an area of 0.01, or 1 hundredth.
The shaded rectangle contains 15 small squares.
So, the area of the shaded rectangle is 15 hundredths, or 0.15.
