Multiplying and dividing by 10, 100 and 1000 are fundamental in our system of arithmetic. These concepts will eventually be used in work involving negative numbers, decimals and percentages so it is important to have a sound understanding of what is going on.
Once again, and I will never get tired of saying it:
NEVER say ‘to multiply by 10 we add a nought.’
This might seem to work for whole numbers, but it leads to misunderstandings with decimals: 3.55 x 10 is not 2.550!
The ideas to get across are;
When multiplying by 10 the digits move one place to the left.
When multiplying by 100 the digits move two places to the left.
When dividing by 10 the digits move one place to the right.
When dividing by 100 the digits move two places to the right.