We're dividing 643950 by 42 
We want to figure out the number of times 643950 can be divided by 42.

Going ahead to step 1:
42 goes into 6 0 times with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 42

Advancing to step 2:
42 can be fit into 64 1 times, resulting in a remainder of 22.
The next digit of our result is 1. 
Result so far: 1.0
If we subtract 42 from 64, we get 22.
Bring next digit (3) of the dividend behind the 22 and repeat the process: 223 / 42

Advancing to step 3:
42 goes into 223 5 times with a remainder of 13.
Record the quotient 5 as the next digit in the result. 
Result so far: 15.0
Subtracting 210 from 223 leaves us with 13.
Bring next digit (9) of the dividend behind the 13 and repeat the process: 139 / 42

Step 4:
If we divide 139 by 42, we get 3 and a remainder of 13.
Use 3 as the next digit of our solution. 
Result so far: 153.0
Deduct 126 from 139 and we're left with 13.
Take the next digit (5) from the dividend and append it to 13, then repeat: 135 / 42

Advancing to step 5:
42 goes into 135 3 times with a remainder of 9.
Use 3 as the next digit of our solution. 
Result so far: 1533.0
If we subtract 126 from 135, we get 9.
Grab the next digit (0) from the dividend, add it to 9, then carry on: 90 / 42

On to step 6:
42 goes into 90 2 times with a remainder of 6.
Record the quotient 2 as the next digit in the result. 
Result so far: 15332.0
If we subtract 84 from 90, we get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Moving on to step 7:
The number 42 fits into 60 1 times, leaving a remainder of 18.
The number 1 becomes the next digit in our result. 
Result so far: 15332.1
Subtracting 42 from 60 leaves us with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 8:
42 can be fit into 180 4 times, resulting in a remainder of 12.
Use 4 as the next digit of our solution. 
Result so far: 15332.14
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 9:
The number 42 fits into 120 2 times, leaving a remainder of 36.
Use 2 as the next digit of our solution. 
Result so far: 15332.142
Subtracting 84 from 120 leaves us with 36.
Since there are no more digits in the dividend, we add a zero to the remainder making it 360, and continue the process.

Step 10:
42 goes into 360 8 times with a remainder of 24.
Use 8 as the next digit of our solution. 
Result so far: 15332.1428
The remainder is 24 after subtracting 336 from 360.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

Let's proceed to step 11:
42 can be fit into 240 5 times, resulting in a remainder of 30.
The next digit of our result is 5. 
Result so far: 15332.14285
Deduct 210 from 240 and we're left with 30.
Since there are no more digits in the dividend, we add a zero to the remainder making it 300, and continue the process.

Let's proceed to step 12:
If we divide 300 by 42, we get 7 and a remainder of 6.
The number 7 becomes the next digit in our result. 
Result so far: 15332.142857
Subtract 294 from 300 to get 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 13:
42 goes into 60 1 times with a remainder of 18.
The next digit of our result is 1. 
Result so far: 15332.1428571
If we take 42 away from 60, we end up with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 14:
When dividing 180 by 42, we get 4 with a remainder of 12.
The number 4 becomes the next digit in our result. 
Result so far: 15332.14285714
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

The final result is 15332.14285714 with a remainder of 1.2e-08.