644840 divided by 20 
The aim is to understand the frequency of 20 in 644840.

Step 1:
The number 20 fits into 6 0 times, leaving a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Include the next digit (4) from the dividend after 6, then repeat: 64 / 20

On to step 2:
The number 20 fits into 64 3 times, leaving a remainder of 4.
Write down 3 as next digit of the result. 
Result so far: 3.0
If we take 60 away from 64, we end up with 4.
Bring next digit (4) of the dividend behind the 4 and repeat the process: 44 / 20

Going ahead to step 3:
20 goes into 44 2 times with a remainder of 4.
Put 2 as the next digit of the answer. 
Result so far: 32.0
Subtract 40 from 44 to get 4.
Grab the next digit (8) from the dividend, add it to 4, then carry on: 48 / 20

Step 4:
20 can be fit into 48 2 times, resulting in a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 322.0
Subtracting 40 from 48 leaves us with 8.
Include the next digit (4) from the dividend after 8, then repeat: 84 / 20

Step 5:
When dividing 84 by 20, we get 4 with a remainder of 4.
Record the quotient 4 as the next digit in the result. 
Result so far: 3224.0
Subtract 80 from 84 to get 4.
Bring next digit (0) of the dividend behind the 4 and repeat the process: 40 / 20

Advancing to step 6:
20 can be fit into 40 2 times, resulting in a remainder of 0.
The next digit of our result is 2. 
Result so far: 32242.0
If we subtract 40 from 40, we 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.

Moving on to step 7:
0 divided by 20 is 0 with a remainder of 0.
Record the quotient 0 as the next digit in the result. 
Result so far: 32242.0
Subtract 0 from 0 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.

Step 8:
20 goes into 0 0 times with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 32242.0
Subtract 0 from 0 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.

Our division results in 32242.0 with a remaining 0.0.