We divide 391991 by 3
We're looking to find how many times 3 goes into 391991.

On to step 1:
3 divided by 3 is 1 with a remainder of 0.
The next digit of our result is 1. 
Result so far: 1.0
Subtract 3 from 3 to get 0.
Grab the next digit (9) from the dividend, add it to 0, then carry on: 9 / 3

Moving on to step 2:
The number 3 fits into 9 3 times, leaving a remainder of 0.
Put 3 as the next digit of the answer. 
Result so far: 13.0
If we take 9 away from 9, we end up with 0.
Append the next digit (1) from the dividend to 0 and continue with: 1 / 3

Let's proceed to step 3:
The number 3 fits into 1 0 times, leaving a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 130.0
Deduct 0 from 1 and we're left with 1.
Append the next digit (9) from the dividend to 1 and continue with: 19 / 3

Advancing to step 4:
3 goes into 19 6 times with a remainder of 1.
Write down 6 as next digit of the result. 
Result so far: 1306.0
The remainder is 1 after subtracting 18 from 19.
Grab the next digit (9) from the dividend, add it to 1, then carry on: 19 / 3

Step 5:
The number 3 fits into 19 6 times, leaving a remainder of 1.
Put 6 as the next digit of the answer. 
Result so far: 13066.0
Subtract 18 from 19 to get 1.
Include the next digit (1) from the dividend after 1, then repeat: 11 / 3

Moving on to step 6:
3 can be fit into 11 3 times, resulting in a remainder of 2.
The number 3 becomes the next digit in our result. 
Result so far: 130663.0
If we take 9 away from 11, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Step 7:
When dividing 20 by 3, we get 6 with a remainder of 2.
Use 6 as the next digit of our solution. 
Result so far: 130663.6
If we take 18 away from 20, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

Advancing to step 8:
3 can be fit into 20 6 times, resulting in a remainder of 2.
The number 6 becomes the next digit in our result. 
Result so far: 130663.66
The remainder is 2 after subtracting 18 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

The final result is 130663.66 with a remainder of 0.002.