We're dividing 421487 by 12 
We want to figure out the number of times 421487 can be divided by 12.

On to step 1:
The number 12 fits into 4 0 times, leaving a remainder of 4.
Use 0 as the next digit of our solution. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Grab the next digit (2) from the dividend, add it to 4, then carry on: 42 / 12

Going ahead to step 2:
When dividing 42 by 12, we get 3 with a remainder of 6.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
The remainder is 6 after subtracting 36 from 42.
Append the next digit (1) from the dividend to 6 and continue with: 61 / 12

Let's proceed to step 3:
If we divide 61 by 12, we get 5 and a remainder of 1.
Write down 5 as next digit of the result. 
Result so far: 35.0
Subtract 60 from 61 to get 1.
Grab the next digit (4) from the dividend, add it to 1, then carry on: 14 / 12

Advancing to step 4:
12 can be fit into 14 1 times, resulting in a remainder of 2.
Put 1 as the next digit of the answer. 
Result so far: 351.0
If we take 12 away from 14, we end up with 2.
Fetch the next digit (8) from the dividend, attach it to 2 and continue: 28 / 12

Let's proceed to step 5:
If we divide 28 by 12, we get 2 and a remainder of 4.
Record the quotient 2 as the next digit in the result. 
Result so far: 3512.0
If we take 24 away from 28, we end up with 4.
Bring next digit (7) of the dividend behind the 4 and repeat the process: 47 / 12

Going ahead to step 6:
If we divide 47 by 12, we get 3 and a remainder of 11.
Write down 3 as next digit of the result. 
Result so far: 35123.0
If we subtract 36 from 47, we get 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 7:
The number 12 fits into 110 9 times, leaving a remainder of 2.
Use 9 as the next digit of our solution. 
Result so far: 35123.9
Subtract 108 from 110 to get 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:
20 divided by 12 is 1 with a remainder of 8.
Use 1 as the next digit of our solution. 
Result so far: 35123.91
The remainder is 8 after subtracting 12 from 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

On to step 9:
80 divided by 12 is 6 with a remainder of 8.
Put 6 as the next digit of the answer. 
Result so far: 35123.916
The remainder is 8 after subtracting 72 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Going ahead to step 10:
12 goes into 80 6 times with a remainder of 8.
Put 6 as the next digit of the answer. 
Result so far: 35123.9166
The remainder is 8 after subtracting 72 from 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The final outcome is 35123.9166, with a leftover of 8e-05.