We're dividing 97212309 by 644 
The aim is to understand the frequency of 644 in 97212309.

On to step 1:
The number 644 fits into 9 0 times, leaving a remainder of 9.
Put 0 as the next digit of the answer. 
Result so far: 0.0
If we subtract 0 from 9, we get 9.
Bring next digit (7) of the dividend behind the 9 and repeat the process: 97 / 644

Going ahead to step 2:
The number 644 fits into 97 0 times, leaving a remainder of 97.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 97, we end up with 97.
Fetch the next digit (2) from the dividend, attach it to 97 and continue: 972 / 644

Let's proceed to step 3:
The number 644 fits into 972 1 times, leaving a remainder of 328.
The next digit of our result is 1. 
Result so far: 1.0
If we take 644 away from 972, we end up with 328.
Bring next digit (1) of the dividend behind the 328 and repeat the process: 3281 / 644

Advancing to step 4:
When dividing 3281 by 644, we get 5 with a remainder of 61.
Write down 5 as next digit of the result. 
Result so far: 15.0
If we subtract 3220 from 3281, we get 61.
Grab the next digit (2) from the dividend, add it to 61, then carry on: 612 / 644

On to step 5:
644 can be fit into 612 0 times, resulting in a remainder of 612.
Write down 0 as next digit of the result. 
Result so far: 150.0
If we take 0 away from 612, we end up with 612.
Include the next digit (3) from the dividend after 612, then repeat: 6123 / 644

Let's proceed to step 6:
644 can be fit into 6123 9 times, resulting in a remainder of 327.
The next digit of our result is 9. 
Result so far: 1509.0
Subtracting 5796 from 6123 leaves us with 327.
Include the next digit (0) from the dividend after 327, then repeat: 3270 / 644

Step 7:
644 goes into 3270 5 times with a remainder of 50.
The number 5 becomes the next digit in our result. 
Result so far: 15095.0
Subtracting 3220 from 3270 leaves us with 50.
Fetch the next digit (9) from the dividend, attach it to 50 and continue: 509 / 644

Step 8:
509 divided by 644 is 0 with a remainder of 509.
Write down 0 as next digit of the result. 
Result so far: 150950.0
If we subtract 0 from 509, we get 509.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5090, and continue the process.

Let's proceed to step 9:
If we divide 5090 by 644, we get 7 and a remainder of 582.
Record the quotient 7 as the next digit in the result. 
Result so far: 150950.7
Deduct 4508 from 5090 and we're left with 582.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5820, and continue the process.

Advancing to step 10:
5820 divided by 644 is 9 with a remainder of 24.
Put 9 as the next digit of the answer. 
Result so far: 150950.79
If we subtract 5796 from 5820, we get 24.
Since there are no more digits in the dividend, we add a zero to the remainder making it 240, and continue the process.

On to step 11:
240 divided by 644 is 0 with a remainder of 240.
Put 0 as the next digit of the answer. 
Result so far: 150950.79
If we subtract 0 from 240, we get 240.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2400, and continue the process.

Going ahead to step 12:
644 goes into 2400 3 times with a remainder of 468.
Use 3 as the next digit of our solution. 
Result so far: 150950.7903
Deduct 1932 from 2400 and we're left with 468.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4680, and continue the process.

Advancing to step 13:
644 goes into 4680 7 times with a remainder of 172.
The next digit of our result is 7. 
Result so far: 150950.79037
Subtract 4508 from 4680 to get 172.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1720, and continue the process.

Advancing to step 14:
644 goes into 1720 2 times with a remainder of 432.
Record the quotient 2 as the next digit in the result. 
Result so far: 150950.790372
Subtract 1288 from 1720 to get 432.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4320, and continue the process.

Let's proceed to step 15:
4320 divided by 644 is 6 with a remainder of 456.
Write down 6 as next digit of the result. 
Result so far: 150950.7903726
If we subtract 3864 from 4320, we get 456.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4560, and continue the process.

Let's proceed to step 16:
The number 644 fits into 4560 7 times, leaving a remainder of 52.
Use 7 as the next digit of our solution. 
Result so far: 150950.79037267
Subtract 4508 from 4560 to get 52.
Since there are no more digits in the dividend, we add a zero to the remainder making it 520, and continue the process.

The final result is 150950.79037267 with a remainder of 5.2e-08.