It's just like how 7x2 helps you solve 7x20. When multiplying a number with another number that's only followed by zeros are simple because all you do is add a zero. Example:
7x2= 14
7x20= 140
7x200= 1400
7x2000= 14000
Etc.
I know there's a term for it, but I forgot because it's been a while since I've learned something like this