3687574 ÷ 643 
The aim is to understand the frequency of 643 in 3687574.

Moving on to step 1:
643 goes into 3 0 times with a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Grab the next digit (6) from the dividend, add it to 3, then carry on: 36 / 643

Going ahead to step 2:
When dividing 36 by 643, we get 0 with a remainder of 36.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 36, we end up with 36.
Grab the next digit (8) from the dividend, add it to 36, then carry on: 368 / 643

Moving on to step 3:
If we divide 368 by 643, we get 0 and a remainder of 368.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 368 after subtracting 0 from 368.
Bring next digit (7) of the dividend behind the 368 and repeat the process: 3687 / 643

Step 4:
If we divide 3687 by 643, we get 5 and a remainder of 472.
The number 5 becomes the next digit in our result. 
Result so far: 5.0
Subtracting 3215 from 3687 leaves us with 472.
Include the next digit (5) from the dividend after 472, then repeat: 4725 / 643

Let's proceed to step 5:
If we divide 4725 by 643, we get 7 and a remainder of 224.
Put 7 as the next digit of the answer. 
Result so far: 57.0
If we take 4501 away from 4725, we end up with 224.
Include the next digit (7) from the dividend after 224, then repeat: 2247 / 643

Advancing to step 6:
If we divide 2247 by 643, we get 3 and a remainder of 318.
The number 3 becomes the next digit in our result. 
Result so far: 573.0
Subtract 1929 from 2247 to get 318.
Include the next digit (4) from the dividend after 318, then repeat: 3184 / 643

Going ahead to step 7:
3184 divided by 643 is 4 with a remainder of 612.
The next digit of our result is 4. 
Result so far: 5734.0
If we take 2572 away from 3184, we end up with 612.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6120, and continue the process.

Let's proceed to step 8:
When dividing 6120 by 643, we get 9 with a remainder of 333.
Put 9 as the next digit of the answer. 
Result so far: 5734.9
If we subtract 5787 from 6120, we get 333.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3330, and continue the process.

Let's proceed to step 9:
The number 643 fits into 3330 5 times, leaving a remainder of 115.
Use 5 as the next digit of our solution. 
Result so far: 5734.95
The remainder is 115 after subtracting 3215 from 3330.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1150, and continue the process.

Advancing to step 10:
643 goes into 1150 1 times with a remainder of 507.
Record the quotient 1 as the next digit in the result. 
Result so far: 5734.951
If we take 643 away from 1150, we end up with 507.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5070, and continue the process.

Advancing to step 11:
If we divide 5070 by 643, we get 7 and a remainder of 569.
Record the quotient 7 as the next digit in the result. 
Result so far: 5734.9517
The remainder is 569 after subtracting 4501 from 5070.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5690, and continue the process.

Advancing to step 12:
643 can be fit into 5690 8 times, resulting in a remainder of 546.
The number 8 becomes the next digit in our result. 
Result so far: 5734.95178
Deduct 5144 from 5690 and we're left with 546.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5460, and continue the process.

Step 13:
If we divide 5460 by 643, we get 8 and a remainder of 316.
The next digit of our result is 8. 
Result so far: 5734.951788
Deduct 5144 from 5460 and we're left with 316.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3160, and continue the process.

The final result is 5734.951788 with a remainder of 3.16e-05.