This method is used when we are multiplying numbers which are near base 10.
First step is to find by how much is the number above 10.
There are 2 parts of the answer, left part (which is most significant part) and right part (which is least significant part). To get right part of the answer, we multiply figures on the right (single digits) vertically. And to get the left part of the answer, we add the 1st number crosswise with 2nd figure or 2nd number crosswise with 1st figure. Since 10 has 1 zero, so there will be 1 digit in the right part.
Note: The number of spaces needed on the right is the number of 0’s in the base number.
For example:
12 x 13
12 is 2 above base 10
13 is 3 above base 10
We write numbers in below fashion.
To get right part, we multiplied 2 with 3.
To get left part, we added crosswise 12 to 3 or 13 to 2.
In this case, there is no carry coming from vertical multiplication of 2 figures on right.
However, I will give you an example where there is a carry coming from vertical multiplication of 2 figures on right.
16 x 13
16 is 6 above base 10
13 is 3 above base 10
To get right part, we multiply 6 with 3, i.e 6 x 3 = 18. 8 becomes right part of answer and carry 1 is moved to left part.
To get left part, we added crosswise 16 to 3 or 13 to 6, and 1 (carry from above), i.e. 16 + 3 + 1 =20.
With this method, we can multiply any pair of numbers which are close to base 10; For example: 12 x 15, 13 x 17, 11 x 14, 12 x 18, 13 x 19 etc.
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