For those who might wonder where the error >>11 is but do not wish to engage, the "5. 1/10/10/...=1/10^n=0" is properly "5. 1/10/10/...=lim[n->inf]1/10^n=0", which is just 0=0 and the lim[n->inf] bit is not subject to handwaving. There is no real number you can multiply "lim[n->inf]1/10^n" with to get 1.