We divide 39900721 by 780
We want to figure out the number of times 39900721 can be divided by 780.

Moving on to step 1:
780 can be fit into 3 0 times, resulting in a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Take the next digit (9) from the dividend and append it to 3, then repeat: 39 / 780

Step 2:
780 can be fit into 39 0 times, resulting in a remainder of 39.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtract 0 from 39 to get 39.
Grab the next digit (9) from the dividend, add it to 39, then carry on: 399 / 780

Going ahead to step 3:
If we divide 399 by 780, we get 0 and a remainder of 399.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 399, we end up with 399.
Take the next digit (0) from the dividend and append it to 399, then repeat: 3990 / 780

Going ahead to step 4:
If we divide 3990 by 780, we get 5 and a remainder of 90.
Write down 5 as next digit of the result. 
Result so far: 5.0
The remainder is 90 after subtracting 3900 from 3990.
Fetch the next digit (0) from the dividend, attach it to 90 and continue: 900 / 780

Moving on to step 5:
The number 780 fits into 900 1 times, leaving a remainder of 120.
Use 1 as the next digit of our solution. 
Result so far: 51.0
Subtract 780 from 900 to get 120.
Include the next digit (7) from the dividend after 120, then repeat: 1207 / 780

Let's proceed to step 6:
780 can be fit into 1207 1 times, resulting in a remainder of 427.
Record the quotient 1 as the next digit in the result. 
Result so far: 511.0
If we subtract 780 from 1207, we get 427.
Append the next digit (2) from the dividend to 427 and continue with: 4272 / 780

Advancing to step 7:
780 goes into 4272 5 times with a remainder of 372.
Use 5 as the next digit of our solution. 
Result so far: 5115.0
Subtract 3900 from 4272 to get 372.
Fetch the next digit (1) from the dividend, attach it to 372 and continue: 3721 / 780

Moving on to step 8:
If we divide 3721 by 780, we get 4 and a remainder of 601.
Record the quotient 4 as the next digit in the result. 
Result so far: 51154.0
The remainder is 601 after subtracting 3120 from 3721.
Since there are no more digits in the dividend, we add a zero to the remainder making it 6010, and continue the process.

On to step 9:
When dividing 6010 by 780, we get 7 with a remainder of 550.
The number 7 becomes the next digit in our result. 
Result so far: 51154.7
Subtracting 5460 from 6010 leaves us with 550.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5500, and continue the process.

Step 10:
If we divide 5500 by 780, we get 7 and a remainder of 40.
Put 7 as the next digit of the answer. 
Result so far: 51154.77
Subtracting 5460 from 5500 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.

Our division results in 51154.77 with a remaining 0.04.