We look at the division of 393509 by 87 
The aim is to understand the frequency of 87 in 393509.

Moving on to step 1:
87 can be fit into 3 0 times, resulting in a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 3 and we're left with 3.
Append the next digit (9) from the dividend to 3 and continue with: 39 / 87

Moving on to step 2:
39 divided by 87 is 0 with a remainder of 39.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we subtract 0 from 39, we get 39.
Take the next digit (3) from the dividend and append it to 39, then repeat: 393 / 87

Going ahead to step 3:
87 can be fit into 393 4 times, resulting in a remainder of 45.
The next digit of our result is 4. 
Result so far: 4.0
Deduct 348 from 393 and we're left with 45.
Include the next digit (5) from the dividend after 45, then repeat: 455 / 87

Step 4:
455 divided by 87 is 5 with a remainder of 20.
Put 5 as the next digit of the answer. 
Result so far: 45.0
Subtracting 435 from 455 leaves us with 20.
Grab the next digit (0) from the dividend, add it to 20, then carry on: 200 / 87

Going ahead to step 5:
200 divided by 87 is 2 with a remainder of 26.
The number 2 becomes the next digit in our result. 
Result so far: 452.0
If we subtract 174 from 200, we get 26.
Include the next digit (9) from the dividend after 26, then repeat: 269 / 87

Going ahead to step 6:
The number 87 fits into 269 3 times, leaving a remainder of 8.
The next digit of our result is 3. 
Result so far: 4523.0
If we subtract 261 from 269, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Step 7:
When dividing 80 by 87, we get 0 with a remainder of 80.
Put 0 as the next digit of the answer. 
Result so far: 4523.0
Subtracting 0 from 80 leaves us with 80.
Since there are no more digits in the dividend, we add a zero to the remainder making it 800, and continue the process.

Let's proceed to step 8:
If we divide 800 by 87, we get 9 and a remainder of 17.
The number 9 becomes the next digit in our result. 
Result so far: 4523.09
Deduct 783 from 800 and we're left 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.

Let's proceed to step 9:
When dividing 170 by 87, we get 1 with a remainder of 83.
The next digit of our result is 1. 
Result so far: 4523.091
If we take 87 away from 170, we end up with 83.
Since there are no more digits in the dividend, we add a zero to the remainder making it 830, and continue the process.

Advancing to step 10:
87 can be fit into 830 9 times, resulting in a remainder of 47.
The number 9 becomes the next digit in our result. 
Result so far: 4523.0919
If we take 783 away from 830, we end up with 47.
Since there are no more digits in the dividend, we add a zero to the remainder making it 470, and continue the process.

Step 11:
470 divided by 87 is 5 with a remainder of 35.
The number 5 becomes the next digit in our result. 
Result so far: 4523.09195
Subtract 435 from 470 to get 35.
Since there are no more digits in the dividend, we add a zero to the remainder making it 350, and continue the process.

Step 12:
When dividing 350 by 87, we get 4 with a remainder of 2.
The next digit of our result is 4. 
Result so far: 4523.091954
If we subtract 348 from 350, 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.

On to step 13:
20 divided by 87 is 0 with a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 4523.091954
If we take 0 away from 20, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 14:
87 can be fit into 200 2 times, resulting in a remainder of 26.
Put 2 as the next digit of the answer. 
Result so far: 4523.09195402
If we subtract 174 from 200, we get 26.
Since there are no more digits in the dividend, we add a zero to the remainder making it 260, and continue the process.

After the division, we end up with 4523.09195402 and a remainder of 2.6e-08.