We divide 103899 by 21
We want to divide 103899 by 21.

Advancing to step 1:
The number 21 fits into 1 0 times, leaving a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 1, we get 1.
Take the next digit (0) from the dividend and append it to 1, then repeat: 10 / 21

Moving on to step 2:
10 divided by 21 is 0 with a remainder of 10.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 10 leaves us with 10.
Append the next digit (3) from the dividend to 10 and continue with: 103 / 21

Going ahead to step 3:
103 divided by 21 is 4 with a remainder of 19.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Subtracting 84 from 103 leaves us with 19.
Grab the next digit (8) from the dividend, add it to 19, then carry on: 198 / 21

Advancing to step 4:
If we divide 198 by 21, we get 9 and a remainder of 9.
Record the quotient 9 as the next digit in the result. 
Result so far: 49.0
Subtract 189 from 198 to get 9.
Bring next digit (9) of the dividend behind the 9 and repeat the process: 99 / 21

Step 5:
99 divided by 21 is 4 with a remainder of 15.
Write down 4 as next digit of the result. 
Result so far: 494.0
Deduct 84 from 99 and we're left with 15.
Bring next digit (9) of the dividend behind the 15 and repeat the process: 159 / 21

Let's proceed to step 6:
If we divide 159 by 21, we get 7 and a remainder of 12.
Use 7 as the next digit of our solution. 
Result so far: 4947.0
If we take 147 away from 159, we end up with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Let's proceed to step 7:
The number 21 fits into 120 5 times, leaving a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 4947.5
Subtract 105 from 120 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 8:
21 goes into 150 7 times with a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 4947.57
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 9:
If we divide 30 by 21, we get 1 and a remainder of 9.
Write down 1 as next digit of the result. 
Result so far: 4947.571
The remainder is 9 after subtracting 21 from 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Let's proceed to step 10:
90 divided by 21 is 4 with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 4947.5714
Subtracting 84 from 90 leaves us with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Step 11:
21 goes into 60 2 times with a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 4947.57142
The remainder is 18 after subtracting 42 from 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

On to step 12:
21 can be fit into 180 8 times, resulting in a remainder of 12.
The next digit of our result is 8. 
Result so far: 4947.571428
If we subtract 168 from 180, we get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 13:
If we divide 120 by 21, we get 5 and a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 4947.5714285
The remainder is 15 after subtracting 105 from 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

On to step 14:
If we divide 150 by 21, we get 7 and a remainder of 3.
The number 7 becomes the next digit in our result. 
Result so far: 4947.57142857
Subtract 147 from 150 to get 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

In conclusion, the division gives 4947.57142857 with a balance of 3e-09.