644531 divided by 75 
We're looking to find how many times 75 goes into 644531.

Step 1:
When dividing 6 by 75, we get 0 with 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.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 75

On to step 2:
When dividing 64 by 75, we get 0 with a remainder of 64.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 64 after subtracting 0 from 64.
Take the next digit (4) from the dividend and append it to 64, then repeat: 644 / 75

Going ahead to step 3:
75 goes into 644 8 times with a remainder of 44.
The number 8 becomes the next digit in our result. 
Result so far: 8.0
The remainder is 44 after subtracting 600 from 644.
Bring next digit (5) of the dividend behind the 44 and repeat the process: 445 / 75

On to step 4:
If we divide 445 by 75, we get 5 and a remainder of 70.
Use 5 as the next digit of our solution. 
Result so far: 85.0
If we subtract 375 from 445, we get 70.
Grab the next digit (3) from the dividend, add it to 70, then carry on: 703 / 75

Advancing to step 5:
If we divide 703 by 75, we get 9 and a remainder of 28.
The next digit of our result is 9. 
Result so far: 859.0
Subtracting 675 from 703 leaves us with 28.
Grab the next digit (1) from the dividend, add it to 28, then carry on: 281 / 75

Advancing to step 6:
75 can be fit into 281 3 times, resulting in a remainder of 56.
Write down 3 as next digit of the result. 
Result so far: 8593.0
Subtracting 225 from 281 leaves us with 56.
Since there are no more digits in the dividend, we add a zero to the remainder making it 560, and continue the process.

Advancing to step 7:
The number 75 fits into 560 7 times, leaving a remainder of 35.
Use 7 as the next digit of our solution. 
Result so far: 8593.7
Subtracting 525 from 560 leaves us with 35.
Since there are no more digits in the dividend, we add a zero to the remainder making it 350, and continue the process.

Advancing to step 8:
If we divide 350 by 75, we get 4 and a remainder of 50.
Record the quotient 4 as the next digit in the result. 
Result so far: 8593.74
Deduct 300 from 350 and we're left with 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Moving on to step 9:
500 divided by 75 is 6 with a remainder of 50.
The number 6 becomes the next digit in our result. 
Result so far: 8593.746
Subtracting 450 from 500 leaves us with 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

Step 10:
500 divided by 75 is 6 with a remainder of 50.
Put 6 as the next digit of the answer. 
Result so far: 8593.7466
If we subtract 450 from 500, we get 50.
Since there are no more digits in the dividend, we add a zero to the remainder making it 500, and continue the process.

The final result is 8593.7466 with a remainder of 0.0005.