Multiplying & Dividing by 10s

The review section for this topic explains how increasing a number 10-fold makes each piece a piece of the next larger size. For example, 10 tenths make a whole, so if you start with 4 tenths you will get 4 wholes. The reverse is true for division, dividing by tens makes a number smaller.

Instead of moving the numbers to a large or smaller size, a shortcut is to move the decimal point once for each multiple of 10 - making the number larger for multiplication (move right) and smaller for division (move left). An example problem is shown at the right.