We divide 643979 by 40
We want to divide 643979 by 40.

Going ahead to step 1:
If we divide 6 by 40, we get 0 and a remainder of 6.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 6 to get 6.
Take the next digit (4) from the dividend and append it to 6, then repeat: 64 / 40

On to step 2:
When dividing 64 by 40, we get 1 with a remainder of 24.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
Deduct 40 from 64 and we're left with 24.
Fetch the next digit (3) from the dividend, attach it to 24 and continue: 243 / 40

Moving on to step 3:
243 divided by 40 is 6 with a remainder of 3.
Put 6 as the next digit of the answer. 
Result so far: 16.0
If we subtract 240 from 243, we get 3.
Bring next digit (9) of the dividend behind the 3 and repeat the process: 39 / 40

Advancing to step 4:
40 can be fit into 39 0 times, resulting in a remainder of 39.
Use 0 as the next digit of our solution. 
Result so far: 160.0
Deduct 0 from 39 and we're left with 39.
Grab the next digit (7) from the dividend, add it to 39, then carry on: 397 / 40

Going ahead to step 5:
When dividing 397 by 40, we get 9 with a remainder of 37.
The next digit of our result is 9. 
Result so far: 1609.0
If we subtract 360 from 397, we get 37.
Append the next digit (9) from the dividend to 37 and continue with: 379 / 40

Let's proceed to step 6:
When dividing 379 by 40, we get 9 with a remainder of 19.
Put 9 as the next digit of the answer. 
Result so far: 16099.0
If we subtract 360 from 379, 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.

Advancing to step 7:
190 divided by 40 is 4 with a remainder of 30.
Put 4 as the next digit of the answer. 
Result so far: 16099.4
Deduct 160 from 190 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 8:
40 goes into 300 7 times with a remainder of 20.
Use 7 as the next digit of our solution. 
Result so far: 16099.47
Subtracting 280 from 300 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Let's proceed to step 9:
When dividing 200 by 40, we get 5 with a remainder of 0.
Put 5 as the next digit of the answer. 
Result so far: 16099.475
Subtract 200 from 200 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.

Advancing to step 10:
0 divided by 40 is 0 with a remainder of 0.
The next digit of our result is 0. 
Result so far: 16099.475
Deduct 0 from 0 and we're left with 0.
Since there are no more digits in the dividend, we add a zero to the remainder making it 0, and continue the process.

Let's proceed to step 11:
40 goes into 0 0 times with a remainder of 0.
Use 0 as the next digit of our solution. 
Result so far: 16099.475
Subtracting 0 from 0 leaves us with 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 16099.475 with a remaining 0.0.