664031 divided by 90 
The aim is to understand the frequency of 90 in 664031.

Step 1:
If we divide 6 by 90, we get 0 and a remainder of 6.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 6 after subtracting 0 from 6.
Take the next digit (6) from the dividend and append it to 6, then repeat: 66 / 90

On to step 2:
When dividing 66 by 90, we get 0 with a remainder of 66.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 66, we get 66.
Include the next digit (4) from the dividend after 66, then repeat: 664 / 90

Going ahead to step 3:
The number 90 fits into 664 7 times, leaving a remainder of 34.
The next digit of our result is 7. 
Result so far: 7.0
If we take 630 away from 664, we end up with 34.
Take the next digit (0) from the dividend and append it to 34, then repeat: 340 / 90

Let's proceed to step 4:
The number 90 fits into 340 3 times, leaving a remainder of 70.
Use 3 as the next digit of our solution. 
Result so far: 73.0
Subtract 270 from 340 to get 70.
Grab the next digit (3) from the dividend, add it to 70, then carry on: 703 / 90

Going ahead to step 5:
If we divide 703 by 90, we get 7 and a remainder of 73.
Write down 7 as next digit of the result. 
Result so far: 737.0
If we take 630 away from 703, we end up with 73.
Grab the next digit (1) from the dividend, add it to 73, then carry on: 731 / 90

Moving on to step 6:
731 divided by 90 is 8 with a remainder of 11.
Put 8 as the next digit of the answer. 
Result so far: 7378.0
The remainder is 11 after subtracting 720 from 731.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Advancing to step 7:
90 goes into 110 1 times with a remainder of 20.
The next digit of our result is 1. 
Result so far: 7378.1
If we take 90 away from 110, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Going ahead to step 8:
90 can be fit into 200 2 times, resulting in a remainder of 20.
Record the quotient 2 as the next digit in the result. 
Result so far: 7378.12
If we take 180 away from 200, we end up with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Moving on to step 9:
If we divide 200 by 90, we get 2 and a remainder of 20.
Put 2 as the next digit of the answer. 
Result so far: 7378.122
Subtracting 180 from 200 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

The final result is 7378.122 with a remainder of 0.002.