We divide 591090 by 90
The aim is to understand the frequency of 90 in 591090.

On to step 1:
90 can be fit into 5 0 times, resulting in a remainder of 5.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Bring next digit (9) of the dividend behind the 5 and repeat the process: 59 / 90

Going ahead to step 2:
When dividing 59 by 90, we get 0 with a remainder of 59.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 59 to get 59.
Append the next digit (1) from the dividend to 59 and continue with: 591 / 90

Going ahead to step 3:
90 can be fit into 591 6 times, resulting in a remainder of 51.
Put 6 as the next digit of the answer. 
Result so far: 6.0
If we subtract 540 from 591, we get 51.
Fetch the next digit (0) from the dividend, attach it to 51 and continue: 510 / 90

Let's proceed to step 4:
If we divide 510 by 90, we get 5 and a remainder of 60.
Put 5 as the next digit of the answer. 
Result so far: 65.0
If we subtract 450 from 510, we get 60.
Bring next digit (9) of the dividend behind the 60 and repeat the process: 609 / 90

Going ahead to step 5:
If we divide 609 by 90, we get 6 and a remainder of 69.
Use 6 as the next digit of our solution. 
Result so far: 656.0
Deduct 540 from 609 and we're left with 69.
Fetch the next digit (0) from the dividend, attach it to 69 and continue: 690 / 90

Let's proceed to step 6:
90 can be fit into 690 7 times, resulting in a remainder of 60.
The number 7 becomes the next digit in our result. 
Result so far: 6567.0
The remainder is 60 after subtracting 630 from 690.
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:
The number 90 fits into 600 6 times, leaving a remainder of 60.
Record the quotient 6 as the next digit in the result. 
Result so far: 6567.6
Deduct 540 from 600 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.

Advancing to step 8:
90 can be fit into 600 6 times, resulting in a remainder of 60.
The number 6 becomes the next digit in our result. 
Result so far: 6567.66
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.

The quotient of the division is 6567.66, and the remainder is 0.06.