We look at the division of 90643 by 72 
The aim is to understand the frequency of 72 in 90643.

Advancing to step 1:
When dividing 9 by 72, we get 0 with a remainder of 9.
Put 0 as the next digit of the answer. 
Result so far: 0.0
Subtracting 0 from 9 leaves us with 9.
Grab the next digit (0) from the dividend, add it to 9, then carry on: 90 / 72

Moving on to step 2:
72 can be fit into 90 1 times, resulting in a remainder of 18.
The number 1 becomes the next digit in our result. 
Result so far: 1.0
If we take 72 away from 90, we end up with 18.
Take the next digit (6) from the dividend and append it to 18, then repeat: 186 / 72

Advancing to step 3:
72 goes into 186 2 times with a remainder of 42.
Write down 2 as next digit of the result. 
Result so far: 12.0
Deduct 144 from 186 and we're left with 42.
Grab the next digit (4) from the dividend, add it to 42, then carry on: 424 / 72

Step 4:
424 divided by 72 is 5 with a remainder of 64.
Put 5 as the next digit of the answer. 
Result so far: 125.0
If we subtract 360 from 424, we get 64.
Include the next digit (3) from the dividend after 64, then repeat: 643 / 72

Advancing to step 5:
If we divide 643 by 72, we get 8 and a remainder of 67.
Put 8 as the next digit of the answer. 
Result so far: 1258.0
If we subtract 576 from 643, we get 67.
Since there are no more digits in the dividend, we add a zero to the remainder making it 670, and continue the process.

Let's proceed to step 6:
72 goes into 670 9 times with a remainder of 22.
Record the quotient 9 as the next digit in the result. 
Result so far: 1258.9
If we take 648 away from 670, we end up with 22.
Since there are no more digits in the dividend, we add a zero to the remainder making it 220, and continue the process.

On to step 7:
When dividing 220 by 72, we get 3 with a remainder of 4.
Put 3 as the next digit of the answer. 
Result so far: 1258.93
If we take 216 away from 220, we end up with 4.
Since there are no more digits in the dividend, we add a zero to the remainder making it 40, and continue the process.

Moving on to step 8:
If we divide 40 by 72, we get 0 and a remainder of 40.
Write down 0 as next digit of the result. 
Result so far: 1258.93
Subtract 0 from 40 to get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Advancing to step 9:
400 divided by 72 is 5 with a remainder of 40.
Write down 5 as next digit of the result. 
Result so far: 1258.9305
If we subtract 360 from 400, we get 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

On to step 10:
If we divide 400 by 72, we get 5 and a remainder of 40.
The next digit of our result is 5. 
Result so far: 1258.93055
If we take 360 away from 400, we end up with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

After the division, we end up with 1258.93055 and a remainder of 4e-05.