Once you know multiplication and place value, something neat falls out. Multiplying a whole number by 10, 100 or 1000 doesn't change which digits you have — it just moves every digit one, two, or three places to the left.

Each step to the left makes a digit worth ten times as much: ones become tens, tens become hundreds, and so on. Multiplying by 10 shifts everything one place; the empty ones place is then filled with a zero:

Multiplying by 100 shifts two places (two zeros appear), and by 1000 shifts three places (three zeros):

It looks like you are just "adding zeros," but really you are sliding the digits up the place-value columns. The zeros are simply the empty places left behind.

Press play to watch it happen. A number appears in its place-value columns; as we multiply by 10, 100 or 1000, every digit slides left and zeros grow in to fill the empty places. Replay it — a different number and power each time.

Khan Academy works through multiplying by 10, 100 and 1000 here: