8240 divided by 21 
Let's see how many times 21 fits into 8240.

Let's proceed to step 1:
8 divided by 21 is 0 with a remainder of 8.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 8 after subtracting 0 from 8.
Bring next digit (2) of the dividend behind the 8 and repeat the process: 82 / 21

Going ahead to step 2:
21 goes into 82 3 times with a remainder of 19.
Use 3 as the next digit of our solution. 
Result so far: 3.0
Subtracting 63 from 82 leaves us with 19.
Append the next digit (4) from the dividend to 19 and continue with: 194 / 21

On to step 3:
When dividing 194 by 21, we get 9 with a remainder of 5.
Use 9 as the next digit of our solution. 
Result so far: 39.0
Deduct 189 from 194 and we're left with 5.
Take the next digit (0) from the dividend and append it to 5, then repeat: 50 / 21

Step 4:
50 divided by 21 is 2 with a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 392.0
The remainder is 8 after subtracting 42 from 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Advancing to step 5:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Put 3 as the next digit of the answer. 
Result so far: 392.3
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Going ahead to step 6:
21 goes into 170 8 times with a remainder of 2.
The number 8 becomes the next digit in our result. 
Result so far: 392.38
Subtracting 168 from 170 leaves us with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 7:
20 divided by 21 is 0 with a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 392.38
Subtract 0 from 20 to get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Moving on to step 8:
200 divided by 21 is 9 with a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 392.3809
Subtract 189 from 200 to get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Advancing to step 9:
When dividing 110 by 21, we get 5 with a remainder of 5.
The next digit of our result is 5. 
Result so far: 392.38095
Subtract 105 from 110 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Advancing to step 10:
50 divided by 21 is 2 with a remainder of 8.
The number 2 becomes the next digit in our result. 
Result so far: 392.380952
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 11:
21 goes into 80 3 times with a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 392.3809523
If we take 63 away from 80, we end up with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Step 12:
170 divided by 21 is 8 with a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 392.38095238
If we subtract 168 from 170, we get 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

After the division, we end up with 392.38095238 and a remainder of 2e-09.