Let's divide 378450 by 21
The aim is to understand the frequency of 21 in 378450.

Going ahead to step 1:
21 can be fit into 3 0 times, resulting in a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Append the next digit (7) from the dividend to 3 and continue with: 37 / 21

Step 2:
21 goes into 37 1 times with a remainder of 16.
Write down 1 as next digit of the result. 
Result so far: 1.0
Subtract 21 from 37 to get 16.
Fetch the next digit (8) from the dividend, attach it to 16 and continue: 168 / 21

Advancing to step 3:
When dividing 168 by 21, we get 8 with a remainder of 0.
Put 8 as the next digit of the answer. 
Result so far: 18.0
Subtract 168 from 168 to get 0.
Bring next digit (4) of the dividend behind the 0 and repeat the process: 4 / 21

Going ahead to step 4:
If we divide 4 by 21, we get 0 and a remainder of 4.
Write down 0 as next digit of the result. 
Result so far: 180.0
Deduct 0 from 4 and we're left with 4.
Grab the next digit (5) from the dividend, add it to 4, then carry on: 45 / 21

Advancing to step 5:
45 divided by 21 is 2 with a remainder of 3.
The next digit of our result is 2. 
Result so far: 1802.0
Deduct 42 from 45 and we're left with 3.
Take the next digit (0) from the dividend and append it to 3, then repeat: 30 / 21

Let's proceed to step 6:
30 divided by 21 is 1 with a remainder of 9.
The next digit of our result is 1. 
Result so far: 18021.0
Subtracting 21 from 30 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Going ahead to step 7:
When dividing 90 by 21, we get 4 with a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 18021.4
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

On to step 8:
The number 21 fits into 60 2 times, leaving a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 18021.42
If we take 42 away from 60, we end up with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Step 9:
The number 21 fits into 180 8 times, leaving a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 18021.428
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Moving on to step 10:
If we divide 120 by 21, we get 5 and a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 18021.4285
If we take 105 away from 120, we end up with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Advancing to step 11:
When dividing 150 by 21, we get 7 with a remainder of 3.
The next digit of our result is 7. 
Result so far: 18021.42857
Subtracting 147 from 150 leaves us with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

Going ahead to step 12:
When dividing 30 by 21, we get 1 with a remainder of 9.
Put 1 as the next digit of the answer. 
Result so far: 18021.428571
Deduct 21 from 30 and we're left with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Going ahead to step 13:
21 can be fit into 90 4 times, resulting in a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 18021.4285714
Deduct 84 from 90 and we're left with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 14:
If we divide 60 by 21, we get 2 and a remainder of 18.
The number 2 becomes the next digit in our result. 
Result so far: 18021.42857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

After the division, we end up with 18021.42857142 and a remainder of 1.8e-08.