In this tutorial we will subtract the binary number 101012 from 11102 using the borrow method.



  1. First, we subtract the rightmost column. 1 minus 0 equals 1.
    10101
  - 01110
        1
  1. In order to subtract the second column, we need to borrow a 1. So we cross out the 1 in the third column, and represent it as two 1s in the second column.
       1
      01
    10101
  - 01110
        1
  1. We can now subtract 1 from the group of two borrowed 1s. This leaves us with 1, so we write it below the second column.
       1
      01
    10101
  - 01110
       11
  1. Now we subtract the next column. Since we borrowed from this column, the subtraction is 0 minus 1 and we must borrow again. However, our next column has no 1 for us to borrow. So, we must first borrow from the last column.
     1 1
    0101
    10101
  - 01110
       11
  1. Then borrow a 1 from the fourth column into our current column.
      1
     111
    0101
    10101
  - 01110
       11
  1. We can now perform the subtraction for the current column. We take 1 away from our group of two blue 1s. This leaves us with a single 1 which we write below the column.
      1
     111
    0101
    10101
  - 01110
      111
  1. In the fourth column, we subtract 1 from 1 for a result of 0.
      1
     111
    0101
    10101
  - 01110
     0111
  1. Our last column contains contains all zeros, so we write 0 below it. This gives us our answer of 001112.
      1
     111
    0101
    10101
  - 01110
    00111

Animated version