644940 ÷ 80 
We're looking to find how many times 80 goes into 644940.

Going ahead to step 1:
The number 80 fits into 6 0 times, leaving a remainder of 6.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 80

Moving on to step 2:
80 goes into 64 0 times with a remainder of 64.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 64, we get 64.
Append the next digit (4) from the dividend to 64 and continue with: 644 / 80

Going ahead to step 3:
80 can be fit into 644 8 times, resulting in a remainder of 4.
Write down 8 as next digit of the result. 
Result so far: 8.0
Subtract 640 from 644 to get 4.
Fetch the next digit (9) from the dividend, attach it to 4 and continue: 49 / 80

Moving on to step 4:
If we divide 49 by 80, we get 0 and a remainder of 49.
Put 0 as the next digit of the answer. 
Result so far: 80.0
Subtracting 0 from 49 leaves us with 49.
Fetch the next digit (4) from the dividend, attach it to 49 and continue: 494 / 80

Advancing to step 5:
80 goes into 494 6 times with a remainder of 14.
Use 6 as the next digit of our solution. 
Result so far: 806.0
If we subtract 480 from 494, we get 14.
Fetch the next digit (0) from the dividend, attach it to 14 and continue: 140 / 80

Going ahead to step 6:
140 divided by 80 is 1 with a remainder of 60.
Write down 1 as next digit of the result. 
Result so far: 8061.0
If we take 80 away from 140, we end up with 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Let's proceed to step 7:
80 goes into 600 7 times with a remainder of 40.
Put 7 as the next digit of the answer. 
Result so far: 8061.7
Subtracting 560 from 600 leaves us with 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 8:
80 can be fit into 400 5 times, resulting in a remainder of 0.
Put 5 as the next digit of the answer. 
Result so far: 8061.75
If we subtract 400 from 400, we 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.

Going ahead to step 9:
80 goes into 0 0 times with a remainder of 0.
Write down 0 as next digit of the result. 
Result so far: 8061.75
Subtract 0 from 0 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.

Going ahead to step 10:
The number 80 fits into 0 0 times, leaving a remainder of 0.
The next digit of our result is 0. 
Result so far: 8061.75
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.

The final outcome is 8061.75, with a leftover of 0.0.