Times 11 and + 10% Charge

1. Any number multiplied by 11

15 x 11 = ?

Take 1 as first digit and 5 as last digit of the answer, then add the digits for the middle number.

15 x 11 = 1   1+5   5

15 x 11 = 1     6     5

15 x 11 = 1 6 5

For more than 2 digits:

1726 x 11 = ?

Take 1 as first digit and 6 as the last digit of the answer. Then add every two adjacent digits for the middle numbers.

1726 x 11 = ?

1726 x 11 = 1    1+7   7+2   2+6     6

1726 x 11 = 1      8       9        8       6

1726 x 11 = 18986

2. Cost + 10% charge

For anything that will cost you an additional 10% charge, same procedure as above but take the last digit as decimal. Because adding 10% is same as multiplying 110% equal to 1.1 in decimal form.

15 + 10% charge = ?

15 x 1.1 = 1   1+5   .5

15 x 1.1 = 1      6    .5

15 x 1.1 = 16.5

1726 x 1.1 = ?

1726 x 1.1 = 1    1+7   7+2   2+6    .6

1726 x 1.1 = 1      8       9        8      .6

1726 x 1.1 = 1898.6

3. When sums of digits are greater than 9, take only the ones digit and add 1 to the preceding number.

472 x 11 = ?

472 x 11 = 4    4+7    7+2    2

472 x 11 = 4     11*     9       2

472 x 11 = 5*     1       9       2

472 x 11 = 5192

164 x 1.1 = ?

164 x 1.1 = 1   1+6    6+4   .4

164 x 1.1 = 1      7      10    .4

164 x 1.1 = 1      8       0     .4

164 x 1.1 = 180.4

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