We're dividing 12840399 by 100 
We want to divide 12840399 by 100.

Moving on to step 1:
100 goes into 1 0 times with a remainder of 1.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 1, we end up with 1.
Take the next digit (2) from the dividend and append it to 1, then repeat: 12 / 100

Let's proceed to step 2:
When dividing 12 by 100, we get 0 with a remainder of 12.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 12 leaves us with 12.
Fetch the next digit (8) from the dividend, attach it to 12 and continue: 128 / 100

Moving on to step 3:
100 goes into 128 1 times with a remainder of 28.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
Subtract 100 from 128 to get 28.
Append the next digit (4) from the dividend to 28 and continue with: 284 / 100

Going ahead to step 4:
If we divide 284 by 100, we get 2 and a remainder of 84.
Record the quotient 2 as the next digit in the result. 
Result so far: 12.0
If we take 200 away from 284, we end up with 84.
Take the next digit (0) from the dividend and append it to 84, then repeat: 840 / 100

Let's proceed to step 5:
When dividing 840 by 100, we get 8 with a remainder of 40.
Use 8 as the next digit of our solution. 
Result so far: 128.0
Subtract 800 from 840 to get 40.
Take the next digit (3) from the dividend and append it to 40, then repeat: 403 / 100

Going ahead to step 6:
100 can be fit into 403 4 times, resulting in a remainder of 3.
The number 4 becomes the next digit in our result. 
Result so far: 1284.0
Subtract 400 from 403 to get 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 100

On to step 7:
100 can be fit into 39 0 times, resulting in a remainder of 39.
Record the quotient 0 as the next digit in the result. 
Result so far: 12840.0
The remainder is 39 after subtracting 0 from 39.
Take the next digit (9) from the dividend and append it to 39, then repeat: 399 / 100

On to step 8:
100 can be fit into 399 3 times, resulting in a remainder of 99.
Record the quotient 3 as the next digit in the result. 
Result so far: 128403.0
Subtracting 300 from 399 leaves us with 99.
Since there are no more digits in the dividend, we add a zero to the remainder making it 990, and continue the process.

Going ahead to step 9:
The number 100 fits into 990 9 times, leaving a remainder of 90.
Write down 9 as next digit of the result. 
Result so far: 128403.9
The remainder is 90 after subtracting 900 from 990.
Since there are no more digits in the dividend, we add a zero to the remainder making it 900, and continue the process.

Going ahead to step 10:
900 divided by 100 is 9 with a remainder of 0.
Put 9 as the next digit of the answer. 
Result so far: 128403.99
Subtract 900 from 900 to get 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

The final outcome is 128403.99, with a leftover of 0.0.