We look at the division of 78931309 by 421 
Our goal is to divide 78931309 by 421.

Step 1:
421 goes into 7 0 times with a remainder of 7.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we take 0 away from 7, we end up with 7.
Take the next digit (8) from the dividend and append it to 7, then repeat: 78 / 421

Step 2:
78 divided by 421 is 0 with a remainder of 78.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 78 after subtracting 0 from 78.
Take the next digit (9) from the dividend and append it to 78, then repeat: 789 / 421

Step 3:
789 divided by 421 is 1 with a remainder of 368.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 421 away from 789, we end up with 368.
Append the next digit (3) from the dividend to 368 and continue with: 3683 / 421

Let's proceed to step 4:
If we divide 3683 by 421, we get 8 and a remainder of 315.
Write down 8 as next digit of the result. 
Result so far: 18.0
If we take 3368 away from 3683, we end up with 315.
Bring next digit (1) of the dividend behind the 315 and repeat the process: 3151 / 421

Going ahead to step 5:
When dividing 3151 by 421, we get 7 with a remainder of 204.
Write down 7 as next digit of the result. 
Result so far: 187.0
If we subtract 2947 from 3151, we get 204.
Take the next digit (3) from the dividend and append it to 204, then repeat: 2043 / 421

Let's proceed to step 6:
421 goes into 2043 4 times with a remainder of 359.
Put 4 as the next digit of the answer. 
Result so far: 1874.0
If we take 1684 away from 2043, we end up with 359.
Fetch the next digit (0) from the dividend, attach it to 359 and continue: 3590 / 421

Let's proceed to step 7:
The number 421 fits into 3590 8 times, leaving a remainder of 222.
The number 8 becomes the next digit in our result. 
Result so far: 18748.0
If we take 3368 away from 3590, we end up with 222.
Bring next digit (9) of the dividend behind the 222 and repeat the process: 2229 / 421

Let's proceed to step 8:
2229 divided by 421 is 5 with a remainder of 124.
Put 5 as the next digit of the answer. 
Result so far: 187485.0
Subtracting 2105 from 2229 leaves us with 124.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1240, and continue the process.

Let's proceed to step 9:
421 can be fit into 1240 2 times, resulting in a remainder of 398.
The number 2 becomes the next digit in our result. 
Result so far: 187485.2
Subtracting 842 from 1240 leaves us with 398.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3980, and continue the process.

Let's proceed to step 10:
The number 421 fits into 3980 9 times, leaving a remainder of 191.
The next digit of our result is 9. 
Result so far: 187485.29
If we take 3789 away from 3980, we end up with 191.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1910, and continue the process.

Let's proceed to step 11:
421 goes into 1910 4 times with a remainder of 226.
Record the quotient 4 as the next digit in the result. 
Result so far: 187485.294
If we take 1684 away from 1910, we end up with 226.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2260, and continue the process.

On to step 12:
421 can be fit into 2260 5 times, resulting in a remainder of 155.
Write down 5 as next digit of the result. 
Result so far: 187485.2945
Subtract 2105 from 2260 to get 155.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1550, and continue the process.

Let's proceed to step 13:
421 can be fit into 1550 3 times, resulting in a remainder of 287.
The number 3 becomes the next digit in our result. 
Result so far: 187485.29453
Subtracting 1263 from 1550 leaves us with 287.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2870, and continue the process.

On to step 14:
The number 421 fits into 2870 6 times, leaving a remainder of 344.
Record the quotient 6 as the next digit in the result. 
Result so far: 187485.294536
If we take 2526 away from 2870, we end up with 344.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3440, and continue the process.

On to step 15:
When dividing 3440 by 421, we get 8 with a remainder of 72.
Write down 8 as next digit of the result. 
Result so far: 187485.2945368
Subtract 3368 from 3440 to get 72.
Since there are no more digits in the dividend, we add a zero to the remainder making it 720, and continue the process.

Moving on to step 16:
If we divide 720 by 421, we get 1 and a remainder of 299.
The next digit of our result is 1. 
Result so far: 187485.29453681
Subtracting 421 from 720 leaves us with 299.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2990, and continue the process.

The final outcome is 187485.29453681, with a leftover of 2.99e-07.