We divide 643664 by 15
The aim is to understand the frequency of 15 in 643664.

Advancing to step 1:
15 goes into 6 0 times with a remainder of 6.
Write down 0 as next digit of the result. 
Result so far: 0.0
If we take 0 away from 6, we end up with 6.
Fetch the next digit (4) from the dividend, attach it to 6 and continue: 64 / 15

Let's proceed to step 2:
The number 15 fits into 64 4 times, leaving a remainder of 4.
Use 4 as the next digit of our solution. 
Result so far: 4.0
Subtract 60 from 64 to get 4.
Take the next digit (3) from the dividend and append it to 4, then repeat: 43 / 15

Step 3:
15 can be fit into 43 2 times, resulting in a remainder of 13.
Use 2 as the next digit of our solution. 
Result so far: 42.0
If we subtract 30 from 43, we get 13.
Include the next digit (6) from the dividend after 13, then repeat: 136 / 15

Let's proceed to step 4:
136 divided by 15 is 9 with a remainder of 1.
The next digit of our result is 9. 
Result so far: 429.0
If we take 135 away from 136, we end up with 1.
Append the next digit (6) from the dividend to 1 and continue with: 16 / 15

On to step 5:
15 goes into 16 1 times with a remainder of 1.
Record the quotient 1 as the next digit in the result. 
Result so far: 4291.0
If we subtract 15 from 16, we get 1.
Grab the next digit (4) from the dividend, add it to 1, then carry on: 14 / 15

Going ahead to step 6:
15 goes into 14 0 times with a remainder of 14.
Record the quotient 0 as the next digit in the result. 
Result so far: 42910.0
The remainder is 14 after subtracting 0 from 14.
Since there are no more digits in the dividend, we add a zero to the remainder making it 140, and continue the process.

Step 7:
If we divide 140 by 15, we get 9 and a remainder of 5.
Record the quotient 9 as the next digit in the result. 
Result so far: 42910.9
If we take 135 away from 140, 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.

Going ahead to step 8:
15 can be fit into 50 3 times, resulting in a remainder of 5.
The next digit of our result is 3. 
Result so far: 42910.93
If we subtract 45 from 50, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Let's proceed to step 9:
15 can be fit into 50 3 times, resulting in a remainder of 5.
The next digit of our result is 3. 
Result so far: 42910.933
Subtract 45 from 50 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Our division results in 42910.933 with a remaining 0.0005.