643948 divided by 39 
The aim is to understand the frequency of 39 in 643948.

Step 1:
6 divided by 39 is 0 with 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.
Fetch the next digit (4) from the dividend, attach it to 6 and continue: 64 / 39

Going ahead to step 2:
If we divide 64 by 39, we get 1 and a remainder of 25.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtracting 39 from 64 leaves us with 25.
Grab the next digit (3) from the dividend, add it to 25, then carry on: 253 / 39

Moving on to step 3:
When dividing 253 by 39, we get 6 with a remainder of 19.
Write down 6 as next digit of the result. 
Result so far: 16.0
Subtract 234 from 253 to get 19.
Take the next digit (9) from the dividend and append it to 19, then repeat: 199 / 39

On to step 4:
When dividing 199 by 39, we get 5 with a remainder of 4.
Write down 5 as next digit of the result. 
Result so far: 165.0
Subtract 195 from 199 to get 4.
Fetch the next digit (4) from the dividend, attach it to 4 and continue: 44 / 39

Advancing to step 5:
39 goes into 44 1 times with a remainder of 5.
The number 1 becomes the next digit in our result. 
Result so far: 1651.0
The remainder is 5 after subtracting 39 from 44.
Include the next digit (8) from the dividend after 5, then repeat: 58 / 39

Advancing to step 6:
If we divide 58 by 39, we get 1 and a remainder of 19.
Put 1 as the next digit of the answer. 
Result so far: 16511.0
If we take 39 away from 58, we end up with 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Moving on to step 7:
The number 39 fits into 190 4 times, leaving a remainder of 34.
Record the quotient 4 as the next digit in the result. 
Result so far: 16511.4
Subtracting 156 from 190 leaves us with 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

Advancing to step 8:
340 divided by 39 is 8 with a remainder of 28.
The number 8 becomes the next digit in our result. 
Result so far: 16511.48
Deduct 312 from 340 and we're left with 28.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

Step 9:
When dividing 280 by 39, we get 7 with a remainder of 7.
Use 7 as the next digit of our solution. 
Result so far: 16511.487
If we subtract 273 from 280, we get 7.
Since there are no more digits in the dividend, we add a zero to the remainder making it 70, and continue the process.

Let's proceed to step 10:
When dividing 70 by 39, we get 1 with a remainder of 31.
Record the quotient 1 as the next digit in the result. 
Result so far: 16511.4871
Subtract 39 from 70 to get 31.
Since there are no more digits in the dividend, we add a zero to the remainder making it 310, and continue the process.

Going ahead to step 11:
When dividing 310 by 39, we get 7 with a remainder of 37.
The next digit of our result is 7. 
Result so far: 16511.48717
Subtract 273 from 310 to get 37.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Let's proceed to step 12:
39 goes into 370 9 times with a remainder of 19.
The number 9 becomes the next digit in our result. 
Result so far: 16511.487179
If we subtract 351 from 370, we get 19.
Since there are no more digits in the dividend, we add a zero to the remainder making it 190, and continue the process.

Step 13:
190 divided by 39 is 4 with a remainder of 34.
The next digit of our result is 4. 
Result so far: 16511.4871794
If we take 156 away from 190, we end up with 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

Step 14:
If we divide 340 by 39, we get 8 and a remainder of 28.
The next digit of our result is 8. 
Result so far: 16511.48717948
The remainder is 28 after subtracting 312 from 340.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

The final result is 16511.48717948 with a remainder of 2.8e-08.