578458 ÷ 15 
The aim is to understand the frequency of 15 in 578458.

On to step 1:
When dividing 5 by 15, we get 0 with a remainder of 5.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Include the next digit (7) from the dividend after 5, then repeat: 57 / 15

Going ahead to step 2:
57 divided by 15 is 3 with a remainder of 12.
Put 3 as the next digit of the answer. 
Result so far: 3.0
Subtracting 45 from 57 leaves us with 12.
Take the next digit (8) from the dividend and append it to 12, then repeat: 128 / 15

Step 3:
15 goes into 128 8 times with a remainder of 8.
Record the quotient 8 as the next digit in the result. 
Result so far: 38.0
If we subtract 120 from 128, we get 8.
Grab the next digit (4) from the dividend, add it to 8, then carry on: 84 / 15

Step 4:
The number 15 fits into 84 5 times, leaving a remainder of 9.
The number 5 becomes the next digit in our result. 
Result so far: 385.0
Deduct 75 from 84 and we're left with 9.
Include the next digit (5) from the dividend after 9, then repeat: 95 / 15

Step 5:
15 goes into 95 6 times with a remainder of 5.
Put 6 as the next digit of the answer. 
Result so far: 3856.0
Subtracting 90 from 95 leaves us with 5.
Fetch the next digit (8) from the dividend, attach it to 5 and continue: 58 / 15

Moving on to step 6:
15 goes into 58 3 times with a remainder of 13.
Write down 3 as next digit of the result. 
Result so far: 38563.0
Subtract 45 from 58 to get 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Step 7:
130 divided by 15 is 8 with a remainder of 10.
Put 8 as the next digit of the answer. 
Result so far: 38563.8
The remainder is 10 after subtracting 120 from 130.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Let's proceed to step 8:
The number 15 fits into 100 6 times, leaving a remainder of 10.
Write down 6 as next digit of the result. 
Result so far: 38563.86
Subtracting 90 from 100 leaves us with 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Going ahead to step 9:
The number 15 fits into 100 6 times, leaving a remainder of 10.
Write down 6 as next digit of the result. 
Result so far: 38563.866
Subtract 90 from 100 to get 10.
Since there are no more digits in the dividend, we add a zero to the remainder making it 100, and continue the process.

Our division results in 38563.866 with a remaining 0.001.