In this method we are using method of complement.

This method is useful for numbers more than three digits.

Let’s understand this method by taking an example.

**Ex: **3178 – 2398

Divide these numbers into double columns.

Here 98 is greater than 78 so we are adding a complement of 98 in 78.

Complement of 98 = 100 – 98 = 2 (Complement of x = 100 – x)

So 78 + 2 = 80

Add ‘–1’ to the carry.

Now, 31 – 23 = 8

And 8 – 1(Carry) = 7

So the answer is 780.

Let’s take another example.

**Ex: **4523 – 2176

Divide these numbers into double column.

23 is less than 76 so add complement of 76 in 23.

Complement of 76 = 100 – 76 = 24

So 23 + 24 = 47

And add a carry of ‘–1’.

Now 45 – 21 = 24

And 24 – 1(Carry) = 23

So the answer is 2347.