Friday 12 December 2008

Magic Maths multiplying by 11

Multiplying a number by 11.
To multiply any 2-figure number by 11 we just put the total of the two figures between the 2 figures.

Example 1 :
26 x 11 = 286
Notice that the outer figures in 286 are the 26 being multiplied.
And the middle figure is just 2 and 6 added up.

Example 2:
77 x 11 = 847
This involves a carry figure because 7 + 7 = 14
we get 77 x 11 = (7+1)47 = 847

88 * 11 = 968
This involves a carry figure because 8 + 8 = 16
we get 88 x 11 = (8+1)68 = 968

Example 3:
234 x 11 = 2574
We put the 2 and the 4 at the ends.
We add the first pair 2 + 3 = 5.
and we add the last pair: 3 + 4 = 7.

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