The 11 Times Trick We all know the trick when multiplying by ten – add 0 to the end of
the number, but did you know there is an equally easy trick for
multiplying a two digit number by 11? This is it: Take the original number and imagine a space between the two digits (in this example we will use 52:
5_2
Now add the two numbers together and put them in the middle:
5_(5+2)_2
That is it – you have the answer: 572.
If the numbers in the middle add up to a 2 digit number, just insert the second number and add 1 to the first:
