We divide 102243 by 21
We want to figure out the number of times 102243 can be divided by 21.

Going ahead to step 1:
If we divide 1 by 21, we get 0 and a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Grab the next digit (0) from the dividend, add it to 1, then carry on: 10 / 21

On to step 2:
The number 21 fits into 10 0 times, leaving a remainder of 10.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 10, we end up with 10.
Grab the next digit (2) from the dividend, add it to 10, then carry on: 102 / 21

Let's proceed to step 3:
The number 21 fits into 102 4 times, leaving a remainder of 18.
Record the quotient 4 as the next digit in the result. 
Result so far: 4.0
If we take 84 away from 102, we end up with 18.
Fetch the next digit (2) from the dividend, attach it to 18 and continue: 182 / 21

On to step 4:
21 goes into 182 8 times with a remainder of 14.
The next digit of our result is 8. 
Result so far: 48.0
If we subtract 168 from 182, we get 14.
Bring next digit (4) of the dividend behind the 14 and repeat the process: 144 / 21

Advancing to step 5:
The number 21 fits into 144 6 times, leaving a remainder of 18.
The next digit of our result is 6. 
Result so far: 486.0
The remainder is 18 after subtracting 126 from 144.
Fetch the next digit (3) from the dividend, attach it to 18 and continue: 183 / 21

Advancing to step 6:
The number 21 fits into 183 8 times, leaving a remainder of 15.
Record the quotient 8 as the next digit in the result. 
Result so far: 4868.0
If we subtract 168 from 183, we 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.

Step 7:
21 goes into 150 7 times with a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 4868.7
Subtracting 147 from 150 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Advancing to step 8:
If we divide 30 by 21, we get 1 and a remainder of 9.
The number 1 becomes the next digit in our result. 
Result so far: 4868.71
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.

Going ahead to step 9:
21 goes into 90 4 times with a remainder of 6.
The number 4 becomes the next digit in our result. 
Result so far: 4868.714
Deduct 84 from 90 and we're left 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.

Going ahead to step 10:
21 goes into 60 2 times with a remainder of 18.
Use 2 as the next digit of our solution. 
Result so far: 4868.7142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 11:
When dividing 180 by 21, we get 8 with a remainder of 12.
Put 8 as the next digit of the answer. 
Result so far: 4868.71428
Subtracting 168 from 180 leaves us 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.

Advancing to step 12:
21 goes into 120 5 times with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 4868.714285
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Let's proceed to step 13:
If we divide 150 by 21, we get 7 and a remainder of 3.
Use 7 as the next digit of our solution. 
Result so far: 4868.7142857
The remainder is 3 after subtracting 147 from 150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 14:
21 goes into 30 1 times with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 4868.71428571
If we subtract 21 from 30, we get 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

The final outcome is 4868.71428571, with a leftover of 9e-09.