How to calculate average for results

Guys,

A1 B1 C1=B1/A1

A2 B2 C2=B2/A2

A3 B3 C3=B3/A3

A B C = B/A ( not average of ( C1C2C3 ) / 3 )

I have 2 column and I divide one by other..

I need total of 2 columns at the bottom and even that total

should be division of second column by first column..

how is it possible?

Regards

Rajesh