102921 ÷ 90 
The aim is to understand the frequency of 90 in 102921.

Moving on to step 1:
If we divide 1 by 90, we get 0 and a remainder of 1.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 1 leaves us with 1.
Take the next digit (0) from the dividend and append it to 1, then repeat: 10 / 90

Step 2:
If we divide 10 by 90, we get 0 and a remainder of 10.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 10, we end up with 10.
Grab the next digit (2) from the dividend, add it to 10, then carry on: 102 / 90

On to step 3:
If we divide 102 by 90, we get 1 and a remainder of 12.
Write down 1 as next digit of the result. 
Result so far: 1.0
If we subtract 90 from 102, we get 12.
Grab the next digit (9) from the dividend, add it to 12, then carry on: 129 / 90

On to step 4:
90 goes into 129 1 times with a remainder of 39.
Put 1 as the next digit of the answer. 
Result so far: 11.0
If we take 90 away from 129, we end up with 39.
Append the next digit (2) from the dividend to 39 and continue with: 392 / 90

Advancing to step 5:
When dividing 392 by 90, we get 4 with a remainder of 32.
Record the quotient 4 as the next digit in the result. 
Result so far: 114.0
Deduct 360 from 392 and we're left with 32.
Bring next digit (1) of the dividend behind the 32 and repeat the process: 321 / 90

Step 6:
90 goes into 321 3 times with a remainder of 51.
Use 3 as the next digit of our solution. 
Result so far: 1143.0
Subtracting 270 from 321 leaves us with 51.
Since there are no more digits in the dividend, we add a zero to the remainder making it 510, and continue the process.

Step 7:
90 can be fit into 510 5 times, resulting in a remainder of 60.
Put 5 as the next digit of the answer. 
Result so far: 1143.5
Deduct 450 from 510 and we're left with 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Let's proceed to step 8:
90 can be fit into 600 6 times, resulting in a remainder of 60.
The next digit of our result is 6. 
Result so far: 1143.56
If we take 540 away from 600, we end up with 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Moving on to step 9:
90 goes into 600 6 times with a remainder of 60.
The number 6 becomes the next digit in our result. 
Result so far: 1143.566
The remainder is 60 after subtracting 540 from 600.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

After the division, we end up with 1143.566 and a remainder of 0.006.