The answer should not depend on which machine or which pencil you use to
find it. If you work a problem two different ways and get two different answers,
then at least one of them is wrong, and there's a pretty good chance that both
of them are.
(9.99 of anything) + (1.11 of the same thing) = 11.1 of them
9.99 (x 10^-2) + 1.11 (x 10^-2) = 11.1 (x 10^-2) .
Can we do any more with that ?
10^-2 = 1 / 10^2 = 1 / 100 .
11.1 x 10^-2 = 11.1 / 100 = 0.111
