3*3=9,let us take two sets of apple in which first set consists of apple(A,B,C) and second set consists of Apple(1,2,3).If we try to apply multiplication operation between these two sets to get combined number of sets then the results will be A1,A2,A3,B1,B2,B3,C1,C2 and C3. That means there can be made 9 possible sets from this operation. so,1*1=1 and 3*3=9.
