Let's divide 359240 by 21
The aim is to understand the frequency of 21 in 359240.

Advancing to step 1:
3 divided by 21 is 0 with a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we subtract 0 from 3, we get 3.
Bring next digit (5) of the dividend behind the 3 and repeat the process: 35 / 21

Step 2:
If we divide 35 by 21, we get 1 and a remainder of 14.
The next digit of our result is 1. 
Result so far: 1.0
If we take 21 away from 35, we end up with 14.
Bring next digit (9) of the dividend behind the 14 and repeat the process: 149 / 21

Let's proceed to step 3:
21 goes into 149 7 times with a remainder of 2.
Record the quotient 7 as the next digit in the result. 
Result so far: 17.0
Subtract 147 from 149 to get 2.
Take the next digit (2) from the dividend and append it to 2, then repeat: 22 / 21

Going ahead to step 4:
22 divided by 21 is 1 with a remainder of 1.
Put 1 as the next digit of the answer. 
Result so far: 171.0
Deduct 21 from 22 and we're left with 1.
Take the next digit (4) from the dividend and append it to 1, then repeat: 14 / 21

On to step 5:
14 divided by 21 is 0 with a remainder of 14.
Use 0 as the next digit of our solution. 
Result so far: 1710.0
Deduct 0 from 14 and we're left with 14.
Append the next digit (0) from the dividend to 14 and continue with: 140 / 21

Let's proceed to step 6:
When dividing 140 by 21, we get 6 with a remainder of 14.
The next digit of our result is 6. 
Result so far: 17106.0
If we subtract 126 from 140, we get 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

On to step 7:
The number 21 fits into 140 6 times, leaving a remainder of 14.
Write down 6 as next digit of the result. 
Result so far: 17106.6
The remainder is 14 after subtracting 126 from 140.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Step 8:
The number 21 fits into 140 6 times, leaving a remainder of 14.
Write down 6 as next digit of the result. 
Result so far: 17106.66
Subtracting 126 from 140 leaves us with 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

The final outcome is 17106.66, with a leftover of 0.014.