Answer
The trick for multiplying whole numbers by 10, 100, or 1000 is to add however many 0's onto the whole number.
Work Step by Step
For example:
1. $5\times10$ = 50. Since you are multiplying by 10, one 0 is added to the 5
2. $5\times100$ = 500. Since you are multiplying by 100, two 0's are added to the 5
3. $5\times1000$ = 5,000. Since you are multiplying by 1000, three 0's are added to the 5.
...And so on.
