We look at the division of 25101643 by 815 
The aim is to understand the frequency of 815 in 25101643.

Going ahead to step 1:
When dividing 2 by 815, we get 0 with a remainder of 2.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 2, we get 2.
Append the next digit (5) from the dividend to 2 and continue with: 25 / 815

Let's proceed to step 2:
If we divide 25 by 815, we get 0 and a remainder of 25.
Put 0 as the next digit of the answer. 
Result so far: 0.0
The remainder is 25 after subtracting 0 from 25.
Include the next digit (1) from the dividend after 25, then repeat: 251 / 815

Step 3:
If we divide 251 by 815, we get 0 and a remainder of 251.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we subtract 0 from 251, we get 251.
Bring next digit (0) of the dividend behind the 251 and repeat the process: 2510 / 815

Going ahead to step 4:
If we divide 2510 by 815, we get 3 and a remainder of 65.
Use 3 as the next digit of our solution. 
Result so far: 3.0
If we take 2445 away from 2510, we end up with 65.
Append the next digit (1) from the dividend to 65 and continue with: 651 / 815

Going ahead to step 5:
815 goes into 651 0 times with a remainder of 651.
Record the quotient 0 as the next digit in the result. 
Result so far: 30.0
Deduct 0 from 651 and we're left with 651.
Append the next digit (6) from the dividend to 651 and continue with: 6516 / 815

Moving on to step 6:
6516 divided by 815 is 7 with a remainder of 811.
The next digit of our result is 7. 
Result so far: 307.0
The remainder is 811 after subtracting 5705 from 6516.
Grab the next digit (4) from the dividend, add it to 811, then carry on: 8114 / 815

Advancing to step 7:
815 goes into 8114 9 times with a remainder of 779.
Write down 9 as next digit of the result. 
Result so far: 3079.0
If we take 7335 away from 8114, we end up with 779.
Grab the next digit (3) from the dividend, add it to 779, then carry on: 7793 / 815

Step 8:
815 can be fit into 7793 9 times, resulting in a remainder of 458.
Put 9 as the next digit of the answer. 
Result so far: 30799.0
The remainder is 458 after subtracting 7335 from 7793.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4580, and continue the process.

Going ahead to step 9:
815 can be fit into 4580 5 times, resulting in a remainder of 505.
Use 5 as the next digit of our solution. 
Result so far: 30799.5
Subtracting 4075 from 4580 leaves us with 505.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5050, and continue the process.

Moving on to step 10:
815 can be fit into 5050 6 times, resulting in a remainder of 160.
The number 6 becomes the next digit in our result. 
Result so far: 30799.56
Subtract 4890 from 5050 to get 160.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1600, and continue the process.

Let's proceed to step 11:
815 goes into 1600 1 times with a remainder of 785.
The number 1 becomes the next digit in our result. 
Result so far: 30799.561
If we subtract 815 from 1600, we get 785.
Since there are no more digits in the dividend, we add a zero to the remainder making it 7850, and continue the process.

Let's proceed to step 12:
815 goes into 7850 9 times with a remainder of 515.
Write down 9 as next digit of the result. 
Result so far: 30799.5619
If we subtract 7335 from 7850, we get 515.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5150, and continue the process.

On to step 13:
5150 divided by 815 is 6 with a remainder of 260.
The number 6 becomes the next digit in our result. 
Result so far: 30799.56196
If we subtract 4890 from 5150, we get 260.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2600, and continue the process.

On to step 14:
If we divide 2600 by 815, we get 3 and a remainder of 155.
The next digit of our result is 3. 
Result so far: 30799.561963
Subtract 2445 from 2600 to get 155.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1550, and continue the process.

Let's proceed to step 15:
815 goes into 1550 1 times with a remainder of 735.
Record the quotient 1 as the next digit in the result. 
Result so far: 30799.5619631
Deduct 815 from 1550 and we're left with 735.
Since there are no more digits in the dividend, we add a zero to the remainder making it 7350, and continue the process.

Going ahead to step 16:
If we divide 7350 by 815, we get 9 and a remainder of 15.
The number 9 becomes the next digit in our result. 
Result so far: 30799.56196319
Subtract 7335 from 7350 to get 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Our division results in 30799.56196319 with a remaining 1.5e-08.