If I have a 40 % and my teacher puts in 3 100% what's my grade?

It would be an A if i'm correct.

Your grade would be an 85%. The way you do the math is to add the 3 100% together to get 300%. Then you would add the 40% to the 300% to get 340%. After, you would divide that percentage by four since you added only four numbers. When you divided, you would get 85%.