We're dividing 643639 by 91 
We're looking to find how many times 91 goes into 643639.

On to step 1:
The number 91 fits into 6 0 times, leaving a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Bring next digit (4) of the dividend behind the 6 and repeat the process: 64 / 91

Advancing to step 2:
When dividing 64 by 91, we get 0 with a remainder of 64.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 64 to get 64.
Fetch the next digit (3) from the dividend, attach it to 64 and continue: 643 / 91

Advancing to step 3:
When dividing 643 by 91, we get 7 with a remainder of 6.
Put 7 as the next digit of the answer. 
Result so far: 7.0
Deduct 637 from 643 and we're left with 6.
Take the next digit (6) from the dividend and append it to 6, then repeat: 66 / 91

Going ahead to step 4:
The number 91 fits into 66 0 times, leaving a remainder of 66.
Use 0 as the next digit of our solution. 
Result so far: 70.0
Subtract 0 from 66 to get 66.
Include the next digit (3) from the dividend after 66, then repeat: 663 / 91

Let's proceed to step 5:
91 can be fit into 663 7 times, resulting in a remainder of 26.
Use 7 as the next digit of our solution. 
Result so far: 707.0
Deduct 637 from 663 and we're left with 26.
Take the next digit (9) from the dividend and append it to 26, then repeat: 269 / 91

Moving on to step 6:
269 divided by 91 is 2 with a remainder of 87.
Put 2 as the next digit of the answer. 
Result so far: 7072.0
If we take 182 away from 269, we end up with 87.
Since there are no more digits in the dividend, we add a zero to the remainder making it 870, and continue the process.

Going ahead to step 7:
If we divide 870 by 91, we get 9 and a remainder of 51.
Put 9 as the next digit of the answer. 
Result so far: 7072.9
If we subtract 819 from 870, we get 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

On to step 8:
510 divided by 91 is 5 with a remainder of 55.
The number 5 becomes the next digit in our result. 
Result so far: 7072.95
The remainder is 55 after subtracting 455 from 510.
Since there are no more digits in the dividend, we add a zero to the remainder making it 550, and continue the process.

Step 9:
550 divided by 91 is 6 with a remainder of 4.
Put 6 as the next digit of the answer. 
Result so far: 7072.956
If we take 546 away from 550, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 10:
91 goes into 40 0 times with a remainder of 40.
Put 0 as the next digit of the answer. 
Result so far: 7072.956
Subtract 0 from 40 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Going ahead to step 11:
91 can be fit into 400 4 times, resulting in a remainder of 36.
The next digit of our result is 4. 
Result so far: 7072.95604
Subtract 364 from 400 to get 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

On to step 12:
360 divided by 91 is 3 with a remainder of 87.
Record the quotient 3 as the next digit in the result. 
Result so far: 7072.956043
Subtracting 273 from 360 leaves us with 87.
Since there are no more digits in the dividend, we add a zero to the remainder making it 870, and continue the process.

Let's proceed to step 13:
When dividing 870 by 91, we get 9 with a remainder of 51.
Write down 9 as next digit of the result. 
Result so far: 7072.9560439
The remainder is 51 after subtracting 819 from 870.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Step 14:
When dividing 510 by 91, we get 5 with a remainder of 55.
Write down 5 as next digit of the result. 
Result so far: 7072.95604395
Subtracting 455 from 510 leaves us with 55.
Since there are no more digits in the dividend, we add a zero to the remainder making it 550, and continue the process.

In conclusion, the division gives 7072.95604395 with a balance of 5.5e-08.