We look at the division of 649411 by 90 
The aim is to understand the frequency of 90 in 649411.

On to 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
Subtracting 0 from 6 leaves us with 6.
Grab the next digit (4) from the dividend, add it to 6, then carry on: 64 / 90

Let's proceed to step 2:
If we divide 64 by 90, we get 0 and a remainder of 64.
The next digit of our result is 0. 
Result so far: 0.0
If we take 0 away from 64, we end up with 64.
Bring next digit (9) of the dividend behind the 64 and repeat the process: 649 / 90

Going ahead to step 3:
649 divided by 90 is 7 with a remainder of 19.
Record the quotient 7 as the next digit in the result. 
Result so far: 7.0
Deduct 630 from 649 and we're left with 19.
Include the next digit (4) from the dividend after 19, then repeat: 194 / 90

On to step 4:
90 can be fit into 194 2 times, resulting in a remainder of 14.
Use 2 as the next digit of our solution. 
Result so far: 72.0
If we subtract 180 from 194, we get 14.
Grab the next digit (1) from the dividend, add it to 14, then carry on: 141 / 90

On to step 5:
The number 90 fits into 141 1 times, leaving a remainder of 51.
Put 1 as the next digit of the answer. 
Result so far: 721.0
If we take 90 away from 141, we end up with 51.
Append the next digit (1) from the dividend to 51 and continue with: 511 / 90

On to step 6:
When dividing 511 by 90, we get 5 with a remainder of 61.
Use 5 as the next digit of our solution. 
Result so far: 7215.0
Deduct 450 from 511 and we're left with 61.
Since there are no more digits in the dividend, we add a zero to the remainder making it 610, and continue the process.

Advancing to step 7:
The number 90 fits into 610 6 times, leaving a remainder of 70.
The next digit of our result is 6. 
Result so far: 7215.6
If we subtract 540 from 610, we get 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Going ahead to step 8:
The number 90 fits into 700 7 times, leaving a remainder of 70.
Put 7 as the next digit of the answer. 
Result so far: 7215.67
If we take 630 away from 700, we end up with 70.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

On to step 9:
If we divide 700 by 90, we get 7 and a remainder of 70.
Use 7 as the next digit of our solution. 
Result so far: 7215.677
The remainder is 70 after subtracting 630 from 700.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

The final outcome is 7215.677, with a leftover of 0.007.