421337 ÷ 3 
The aim is to understand the frequency of 3 in 421337.

Advancing to step 1:
3 goes into 4 1 times with a remainder of 1.
The next digit of our result is 1. 
Result so far: 1.0
The remainder is 1 after subtracting 3 from 4.
Bring next digit (2) of the dividend behind the 1 and repeat the process: 12 / 3

Advancing to step 2:
If we divide 12 by 3, we get 4 and a remainder of 0.
Use 4 as the next digit of our solution. 
Result so far: 14.0
Deduct 12 from 12 and we're left with 0.
Append the next digit (1) from the dividend to 0 and continue with: 1 / 3

On to step 3:
3 goes into 1 0 times with a remainder of 1.
The number 0 becomes the next digit in our result. 
Result so far: 140.0
Subtract 0 from 1 to get 1.
Include the next digit (3) from the dividend after 1, then repeat: 13 / 3

Let's proceed to step 4:
3 goes into 13 4 times with a remainder of 1.
The next digit of our result is 4. 
Result so far: 1404.0
The remainder is 1 after subtracting 12 from 13.
Grab the next digit (3) from the dividend, add it to 1, then carry on: 13 / 3

On to step 5:
If we divide 13 by 3, we get 4 and a remainder of 1.
Record the quotient 4 as the next digit in the result. 
Result so far: 14044.0
Subtracting 12 from 13 leaves us with 1.
Fetch the next digit (7) from the dividend, attach it to 1 and continue: 17 / 3

Let's proceed to step 6:
3 can be fit into 17 5 times, resulting in a remainder of 2.
The number 5 becomes the next digit in our result. 
Result so far: 140445.0
If we subtract 15 from 17, we 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 7:
When dividing 20 by 3, we get 6 with a remainder of 2.
Record the quotient 6 as the next digit in the result. 
Result so far: 140445.6
Subtract 18 from 20 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.

On to step 8:
The number 3 fits into 20 6 times, leaving a remainder of 2.
The next digit of our result is 6. 
Result so far: 140445.66
Subtracting 18 from 20 leaves us 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.

Our division results in 140445.66 with a remaining 0.002.