Multiplying any number by 101

Multiplying a 2-digit number by 101

Write the 2-digit number next to itself i.e. write the number twice.

Example: 52 × 101 = 5252.

Multiplying numbers more than 2-digit by 101

Rule: First, write the first two digits of the given number as the first two answer digits. Then, starting from the third digit of the given number, add each of the digits of the given number in turn, adding the third digit to the first digit, the fourth digit to the second digit, and so on. When the last digit of the original number is reached, continue writing the remaining digits of the given number.

For example:   164,759 x 101 =?

The first two answer digits are 1 6

Starting from the third digit, 4, add in turn the digits of the given number, 1-6-4-7-5-9.

1 + 4 = 5; 6 + 7 = 13; 4 + 5 = 9; 7 + 9 = 16

The 9 is the last digit of the original given number. Thereafter merely record the balance of the digits of the given number not added: in this case, 5 and 9. Naturally, in the additions performed above, the units digit is recorded as the answer digit; any tens digit is added to the preceding answer digit.

Therefore, 164,759 x 101 = 16,640,659.

So, 1,234,567 x 101 =?

The first two answer digits are 12.

Starting from the third digit; 3, add in turn the digits of the given number, 1-2-3-4-5-6-7.

1 + 3 = 4; 2 + 4 = 6; 3 + 5 = 8; 4 + 6 = 10; 5 + 7 = 12

Now record the balance of the digits of the given number not added: in this case, 6 and 7. In the additions performed above, the units digit is recorded as the answer digit; any tens digit is added to the preceding answer digit.

Therefore, 1,234,567 x 101 = 124,691,267.