51215699 divided by 429 
The aim is to understand the frequency of 429 in 51215699.

On to step 1:
5 divided by 429 is 0 with a remainder of 5.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 5 leaves us with 5.
Take the next digit (1) from the dividend and append it to 5, then repeat: 51 / 429

Moving on to step 2:
51 divided by 429 is 0 with a remainder of 51.
Use 0 as the next digit of our solution. 
Result so far: 0.0
If we take 0 away from 51, we end up with 51.
Take the next digit (2) from the dividend and append it to 51, then repeat: 512 / 429

Advancing to step 3:
If we divide 512 by 429, we get 1 and a remainder of 83.
Record the quotient 1 as the next digit in the result. 
Result so far: 1.0
The remainder is 83 after subtracting 429 from 512.
Take the next digit (1) from the dividend and append it to 83, then repeat: 831 / 429

On to step 4:
429 goes into 831 1 times with a remainder of 402.
Put 1 as the next digit of the answer. 
Result so far: 11.0
Subtract 429 from 831 to get 402.
Fetch the next digit (5) from the dividend, attach it to 402 and continue: 4025 / 429

Let's proceed to step 5:
429 can be fit into 4025 9 times, resulting in a remainder of 164.
The next digit of our result is 9. 
Result so far: 119.0
Subtracting 3861 from 4025 leaves us with 164.
Bring next digit (6) of the dividend behind the 164 and repeat the process: 1646 / 429

Advancing to step 6:
1646 divided by 429 is 3 with a remainder of 359.
Put 3 as the next digit of the answer. 
Result so far: 1193.0
Subtract 1287 from 1646 to get 359.
Append the next digit (9) from the dividend to 359 and continue with: 3599 / 429

Step 7:
If we divide 3599 by 429, we get 8 and a remainder of 167.
Use 8 as the next digit of our solution. 
Result so far: 11938.0
Deduct 3432 from 3599 and we're left with 167.
Append the next digit (9) from the dividend to 167 and continue with: 1679 / 429

Step 8:
1679 divided by 429 is 3 with a remainder of 392.
The next digit of our result is 3. 
Result so far: 119383.0
Deduct 1287 from 1679 and we're left with 392.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3920, and continue the process.

Going ahead to step 9:
If we divide 3920 by 429, we get 9 and a remainder of 59.
Use 9 as the next digit of our solution. 
Result so far: 119383.9
The remainder is 59 after subtracting 3861 from 3920.
Since there are no more digits in the dividend, we add a zero to the remainder making it 590, and continue the process.

Moving on to step 10:
429 goes into 590 1 times with a remainder of 161.
Record the quotient 1 as the next digit in the result. 
Result so far: 119383.91
If we subtract 429 from 590, we get 161.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1610, and continue the process.

Advancing to step 11:
1610 divided by 429 is 3 with a remainder of 323.
Record the quotient 3 as the next digit in the result. 
Result so far: 119383.913
Subtract 1287 from 1610 to get 323.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3230, and continue the process.

Moving on to step 12:
429 goes into 3230 7 times with a remainder of 227.
The next digit of our result is 7. 
Result so far: 119383.9137
The remainder is 227 after subtracting 3003 from 3230.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2270, and continue the process.

Let's proceed to step 13:
429 goes into 2270 5 times with a remainder of 125.
Record the quotient 5 as the next digit in the result. 
Result so far: 119383.91375
If we take 2145 away from 2270, we end up with 125.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1250, and continue the process.

Let's proceed to step 14:
429 can be fit into 1250 2 times, resulting in a remainder of 392.
Record the quotient 2 as the next digit in the result. 
Result so far: 119383.913752
Subtract 858 from 1250 to get 392.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3920, and continue the process.

Step 15:
If we divide 3920 by 429, we get 9 and a remainder of 59.
The number 9 becomes the next digit in our result. 
Result so far: 119383.9137529
Subtract 3861 from 3920 to get 59.
Since there are no more digits in the dividend, we add a zero to the remainder making it 590, and continue the process.

Going ahead to step 16:
The number 429 fits into 590 1 times, leaving a remainder of 161.
The number 1 becomes the next digit in our result. 
Result so far: 119383.91375291
The remainder is 161 after subtracting 429 from 590.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1610, and continue the process.

The final outcome is 119383.91375291, with a leftover of 1.61e-07.