We're dividing 421648 by 20 
Let's see how many times 20 fits into 421648.

Step 1:
If we divide 4 by 20, we get 0 and a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtracting 0 from 4 leaves us with 4.
Grab the next digit (2) from the dividend, add it to 4, then carry on: 42 / 20

On to step 2:
The number 20 fits into 42 2 times, leaving a remainder of 2.
Put 2 as the next digit of the answer. 
Result so far: 2.0
Subtract 40 from 42 to get 2.
Bring next digit (1) of the dividend behind the 2 and repeat the process: 21 / 20

Moving on to step 3:
21 divided by 20 is 1 with a remainder of 1.
The next digit of our result is 1. 
Result so far: 21.0
The remainder is 1 after subtracting 20 from 21.
Take the next digit (6) from the dividend and append it to 1, then repeat: 16 / 20

Going ahead to step 4:
20 goes into 16 0 times with a remainder of 16.
The number 0 becomes the next digit in our result. 
Result so far: 210.0
If we subtract 0 from 16, we get 16.
Fetch the next digit (4) from the dividend, attach it to 16 and continue: 164 / 20

Moving on to step 5:
164 divided by 20 is 8 with a remainder of 4.
The number 8 becomes the next digit in our result. 
Result so far: 2108.0
Deduct 160 from 164 and we're left with 4.
Append the next digit (8) from the dividend to 4 and continue with: 48 / 20

Let's proceed to step 6:
When dividing 48 by 20, we get 2 with a remainder of 8.
Put 2 as the next digit of the answer. 
Result so far: 21082.0
Subtract 40 from 48 to 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.

Moving on to step 7:
20 goes into 80 4 times with a remainder of 0.
Use 4 as the next digit of our solution. 
Result so far: 21082.4
Deduct 80 from 80 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 8:
When dividing 0 by 20, we get 0 with a remainder of 0.
The number 0 becomes the next digit in our result. 
Result so far: 21082.4
Deduct 0 from 0 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Step 9:
20 goes into 0 0 times with a remainder of 0.
Put 0 as the next digit of the answer. 
Result so far: 21082.4
Deduct 0 from 0 and we're left with 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 result is 21082.4 with a remainder of 0.0.