@mary said in Binary Math - CompTIA Network+ N10-007 Prof Messer:

While the math is pretty straightforward, the why would I use this wasn't covered. How often do you use this and for what?

Jared is correct. Basically once you understand how binary makes things work, and knowing how it works in a mask, you never use it. You won't ever need to work in binary, but knowing that it is underneath things helps make something that is super complex, trivially obvious. Basically, if you understand the binary, subnet masking is SO simple. If you don't, it seems like black magic.