We're dividing 691620 by 90 
The aim is to understand the frequency of 90 in 691620.

Going ahead to step 1:
90 can be fit into 6 0 times, resulting in a remainder of 6.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Bring next digit (9) of the dividend behind the 6 and repeat the process: 69 / 90

On to step 2:
The number 90 fits into 69 0 times, leaving a remainder of 69.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 69 after subtracting 0 from 69.
Append the next digit (1) from the dividend to 69 and continue with: 691 / 90

On to step 3:
90 can be fit into 691 7 times, resulting in a remainder of 61.
Use 7 as the next digit of our solution. 
Result so far: 7.0
Deduct 630 from 691 and we're left with 61.
Take the next digit (6) from the dividend and append it to 61, then repeat: 616 / 90

Advancing to step 4:
When dividing 616 by 90, we get 6 with a remainder of 76.
The number 6 becomes the next digit in our result. 
Result so far: 76.0
Subtract 540 from 616 to get 76.
Include the next digit (2) from the dividend after 76, then repeat: 762 / 90

Let's proceed to step 5:
90 goes into 762 8 times with a remainder of 42.
Write down 8 as next digit of the result. 
Result so far: 768.0
Subtract 720 from 762 to get 42.
Grab the next digit (0) from the dividend, add it to 42, then carry on: 420 / 90

Let's proceed to step 6:
The number 90 fits into 420 4 times, leaving a remainder of 60.
The number 4 becomes the next digit in our result. 
Result so far: 7684.0
The remainder is 60 after subtracting 360 from 420.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

Step 7:
If we divide 600 by 90, we get 6 and a remainder of 60.
Put 6 as the next digit of the answer. 
Result so far: 7684.6
Subtract 540 from 600 to get 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

On to step 8:
When dividing 600 by 90, we get 6 with a remainder of 60.
Record the quotient 6 as the next digit in the result. 
Result so far: 7684.66
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.

The final outcome is 7684.66, with a leftover of 0.06.