Is Back Propagation Limited To Only Answer Individual Outputs? (Neural Net coding)

I came across an issue when writing my own neural network. I was messing around with back propagation and noticed it seems to be limited to only being able to correct outputs as if they are the answer themselves.

For example: I was attempting to get my machine to do simple multiplication. I decided to use a single normalized float output that represents 0-1000. No matter how much I trained it on multiplication, it just returned complete trash. But then …

back propagation coding deeplearning neural net