First of all let us consider two number for finding its product. Let it be 13 and 21. We want the answer for 13X21.
1)Let us take the first number that is 13.
2)The number 13 is having two digits 1 and 3.
3)Each digit is represented by lines.
4) First digit is 1 so it can be represented using one line.
5)Second digit is 3 so it can be represented using three lines as shown in below figure.
6)Likewise we can represent the second number 21 with two lines to represent the first digit 2 and one line to represent the second digit 1 as in figure below.
7)Count the number of joints between lines as in below figure.
8) In the left most part the number of joints are 2, in the middle its 6+1=7 and that of right most part is 3.
9) Thus the product of 13X21=273. 