how can i use intergers to estimate each product then calculate each product?
I don't quite understand what you mean by "estimate each product" Do you mean that you want to figure it out in your head roughly? If that is what you mean, then here is a rough way of doing it:
suppose you want to multiply 63 X 45=40 X 60=2400+(40 X3)=2520+(5 X 60)=2820+(5 X3)=2835
