Let S= the set of nonnegative integers less than 10. Consider arbitrary elements (not necessarily distinct) a,b,c,d∈S but with nonzero elements a and c. Then (b×〖10〗^0+a×〖10〗^1 )=(b+10a) and (d×〖10〗^0+c×〖10〗^1 )=(d+10c) are two digits numbers; whose product is (b+10a)×(d+10c)=bd+10bc+10ad+100ac.