Calculating Squares On A Grid

In math we have been learning how to calculate the number of squares on the outside of a 10x10 grid. We have been figuring out ways to figure out the number of squares on the outside of a grid. I will explain two ways to do it, a complex way and a easy way.
First the Complex way:

Find the total number of squares by timesing one side by the other side. Then remove the squares around the outside and times the new side by the other new side. Afterwards minus the smaller number from the bigger number and you have your answer. You can do algebra by changing the ten to n and the 8 to n-2.

Now the easy way:

If the sides are 10 then you can times them by four then you can minus four this works on any number. See told you it was easy, you can also do algebra with this one by changing it to 4n which means 10+10+10+10 minus four.

Now you know how to calculate the square on the outside of a grid, so tell all your friends and act like a nerd if you want to. Also comment any other ways you can think of doing it.