Trick 1 When a number (N) is multiplied by
9,99,999,… or (10n -1).
In such
cases, number of zeros equal to number of 9s in (10n -1) are put
extreme right of N to make a new number M and then N is subtracted from this
new number to get the result. Clearly, (M - N) is the result of multiplication.
Tricks 2 When a number (N) is multiplied by
11, 101, 1001, … or (10n + 1).
In Such a
cases, n zero are put at the right end of N to make a new number M and then N
is added to this new number to get the result. Clearly, M+N is the result of
multiplication.