We divide 329879 by 21
The aim is to understand the frequency of 21 in 329879.

Let's proceed to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 3 after subtracting 0 from 3.
Fetch the next digit (2) from the dividend, attach it to 3 and continue: 32 / 21

Advancing to step 2:
32 divided by 21 is 1 with a remainder of 11.
Use 1 as the next digit of our solution. 
Result so far: 1.0
The remainder is 11 after subtracting 21 from 32.
Include the next digit (9) from the dividend after 11, then repeat: 119 / 21

On to step 3:
If we divide 119 by 21, we get 5 and a remainder of 14.
Record the quotient 5 as the next digit in the result. 
Result so far: 15.0
Subtracting 105 from 119 leaves us with 14.
Take the next digit (8) from the dividend and append it to 14, then repeat: 148 / 21

Moving on to step 4:
21 goes into 148 7 times with a remainder of 1.
Put 7 as the next digit of the answer. 
Result so far: 157.0
Deduct 147 from 148 and we're left with 1.
Take the next digit (7) from the dividend and append it to 1, then repeat: 17 / 21

Advancing to step 5:
The number 21 fits into 17 0 times, leaving a remainder of 17.
The next digit of our result is 0. 
Result so far: 1570.0
The remainder is 17 after subtracting 0 from 17.
Fetch the next digit (9) from the dividend, attach it to 17 and continue: 179 / 21

On to step 6:
21 can be fit into 179 8 times, resulting in a remainder of 11.
The number 8 becomes the next digit in our result. 
Result so far: 15708.0
Subtracting 168 from 179 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Going ahead to step 7:
21 goes into 110 5 times with a remainder of 5.
The next digit of our result is 5. 
Result so far: 15708.5
Subtracting 105 from 110 leaves us with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

On to step 8:
50 divided by 21 is 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 15708.52
If we take 42 away from 50, we end up with 8.
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 9:
The number 21 fits into 80 3 times, leaving a remainder of 17.
Use 3 as the next digit of our solution. 
Result so far: 15708.523
Subtracting 63 from 80 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

On to step 10:
21 goes into 170 8 times with a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 15708.5238
Deduct 168 from 170 and we're left 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.

Moving on to step 11:
If we divide 20 by 21, we get 0 and a remainder of 20.
Use 0 as the next digit of our solution. 
Result so far: 15708.5238
If we subtract 0 from 20, we get 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 12:
When dividing 200 by 21, we get 9 with a remainder of 11.
Record the quotient 9 as the next digit in the result. 
Result so far: 15708.523809
If we subtract 189 from 200, 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.

Going ahead to step 13:
The number 21 fits into 110 5 times, leaving a remainder of 5.
Put 5 as the next digit of the answer. 
Result so far: 15708.5238095
If we take 105 away from 110, we end up with 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Step 14:
If we divide 50 by 21, we get 2 and a remainder of 8.
Write down 2 as next digit of the result. 
Result so far: 15708.52380952
Deduct 42 from 50 and we're left with 8.
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 result is 15708.52380952 with a remainder of 8e-09.