We're dividing 81311321 by 900 
We want to figure out the number of times 81311321 can be divided by 900.

Going ahead to step 1:
If we divide 8 by 900, we get 0 and a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtract 0 from 8 to get 8.
Take the next digit (1) from the dividend and append it to 8, then repeat: 81 / 900

Step 2:
When dividing 81 by 900, we get 0 with a remainder of 81.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Deduct 0 from 81 and we're left with 81.
Grab the next digit (3) from the dividend, add it to 81, then carry on: 813 / 900

Step 3:
The number 900 fits into 813 0 times, leaving a remainder of 813.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 813 to get 813.
Fetch the next digit (1) from the dividend, attach it to 813 and continue: 8131 / 900

Step 4:
When dividing 8131 by 900, we get 9 with a remainder of 31.
Put 9 as the next digit of the answer. 
Result so far: 9.0
Deduct 8100 from 8131 and we're left with 31.
Bring next digit (1) of the dividend behind the 31 and repeat the process: 311 / 900

On to step 5:
311 divided by 900 is 0 with a remainder of 311.
Write down 0 as next digit of the result. 
Result so far: 90.0
Subtracting 0 from 311 leaves us with 311.
Append the next digit (3) from the dividend to 311 and continue with: 3113 / 900

On to step 6:
If we divide 3113 by 900, we get 3 and a remainder of 413.
Record the quotient 3 as the next digit in the result. 
Result so far: 903.0
Deduct 2700 from 3113 and we're left with 413.
Grab the next digit (2) from the dividend, add it to 413, then carry on: 4132 / 900

On to step 7:
If we divide 4132 by 900, we get 4 and a remainder of 532.
Write down 4 as next digit of the result. 
Result so far: 9034.0
If we take 3600 away from 4132, we end up with 532.
Bring next digit (1) of the dividend behind the 532 and repeat the process: 5321 / 900

Advancing to step 8:
5321 divided by 900 is 5 with a remainder of 821.
The next digit of our result is 5. 
Result so far: 90345.0
The remainder is 821 after subtracting 4500 from 5321.
Since there are no more digits in the dividend, we add a zero to the remainder making it 8210, and continue the process.

Let's proceed to step 9:
900 goes into 8210 9 times with a remainder of 110.
Write down 9 as next digit of the result. 
Result so far: 90345.9
Subtract 8100 from 8210 to get 110.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1100, and continue the process.

Advancing to step 10:
If we divide 1100 by 900, we get 1 and a remainder of 200.
Record the quotient 1 as the next digit in the result. 
Result so far: 90345.91
If we take 900 away from 1100, we end up with 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Let's proceed to step 11:
When dividing 2000 by 900, we get 2 with a remainder of 200.
Record the quotient 2 as the next digit in the result. 
Result so far: 90345.912
If we subtract 1800 from 2000, we get 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Going ahead to step 12:
If we divide 2000 by 900, we get 2 and a remainder of 200.
The next digit of our result is 2. 
Result so far: 90345.9122
Deduct 1800 from 2000 and we're left with 200.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2000, and continue the process.

Our division results in 90345.9122 with a remaining 0.002.