Think back to the place value table. What did you notice about the columns? Well, each one is bigger than the one before it. $10$10 units make a ten, $10$10 tens make a hundred, $10$10 hundreds make a thousand and so on, as shown in the picture below.
So when we multiply a number by $10$10, we make it ten times bigger, which means the number moves up a place in the place value table.
A quick way to multiply any whole number by $10$10 is to add a $0$0 at the end.
That moves all our numbers up one place in the place value table, with the $0$0 as a place holder in the units column.
However, this rule is ONLY true for whole numbers, so you have to be careful once fractions or decimals are involved.
Use simple additive strategies with whole numbers and fractions