87877429 ÷ 421 
The aim is to understand the frequency of 421 in 87877429.

Step 1:
421 can be fit into 8 0 times, resulting in a remainder of 8.
Write down 0 as next digit of the result. 
Result so far: 0.0
Deduct 0 from 8 and we're left with 8.
Append the next digit (7) from the dividend to 8 and continue with: 87 / 421

Advancing to step 2:
87 divided by 421 is 0 with a remainder of 87.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 87 to get 87.
Take the next digit (8) from the dividend and append it to 87, then repeat: 878 / 421

On to step 3:
The number 421 fits into 878 2 times, leaving a remainder of 36.
Put 2 as the next digit of the answer. 
Result so far: 2.0
Subtract 842 from 878 to get 36.
Take the next digit (7) from the dividend and append it to 36, then repeat: 367 / 421

On to step 4:
The number 421 fits into 367 0 times, leaving a remainder of 367.
The next digit of our result is 0. 
Result so far: 20.0
Subtract 0 from 367 to get 367.
Grab the next digit (7) from the dividend, add it to 367, then carry on: 3677 / 421

On to step 5:
The number 421 fits into 3677 8 times, leaving a remainder of 309.
The number 8 becomes the next digit in our result. 
Result so far: 208.0
If we take 3368 away from 3677, we end up with 309.
Take the next digit (4) from the dividend and append it to 309, then repeat: 3094 / 421

On to step 6:
The number 421 fits into 3094 7 times, leaving a remainder of 147.
The number 7 becomes the next digit in our result. 
Result so far: 2087.0
Subtract 2947 from 3094 to get 147.
Bring next digit (2) of the dividend behind the 147 and repeat the process: 1472 / 421

Moving on to step 7:
The number 421 fits into 1472 3 times, leaving a remainder of 209.
Write down 3 as next digit of the result. 
Result so far: 20873.0
The remainder is 209 after subtracting 1263 from 1472.
Grab the next digit (9) from the dividend, add it to 209, then carry on: 2099 / 421

Step 8:
421 can be fit into 2099 4 times, resulting in a remainder of 415.
The number 4 becomes the next digit in our result. 
Result so far: 208734.0
If we subtract 1684 from 2099, we get 415.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4150, and continue the process.

Going ahead to step 9:
421 goes into 4150 9 times with a remainder of 361.
Use 9 as the next digit of our solution. 
Result so far: 208734.9
If we subtract 3789 from 4150, we get 361.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3610, and continue the process.

Going ahead to step 10:
421 goes into 3610 8 times with a remainder of 242.
Put 8 as the next digit of the answer. 
Result so far: 208734.98
Subtracting 3368 from 3610 leaves us with 242.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2420, and continue the process.

Step 11:
421 goes into 2420 5 times with a remainder of 315.
The next digit of our result is 5. 
Result so far: 208734.985
Subtracting 2105 from 2420 leaves us with 315.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3150, and continue the process.

Going ahead to step 12:
When dividing 3150 by 421, we get 7 with a remainder of 203.
Write down 7 as next digit of the result. 
Result so far: 208734.9857
The remainder is 203 after subtracting 2947 from 3150.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2030, and continue the process.

Let's proceed to step 13:
421 can be fit into 2030 4 times, resulting in a remainder of 346.
The next digit of our result is 4. 
Result so far: 208734.98574
Subtracting 1684 from 2030 leaves us with 346.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3460, and continue the process.

Let's proceed to step 14:
If we divide 3460 by 421, we get 8 and a remainder of 92.
Put 8 as the next digit of the answer. 
Result so far: 208734.985748
If we subtract 3368 from 3460, we get 92.
Since there are no more digits in the dividend, we add a zero to the remainder making it 920, and continue the process.

Advancing to step 15:
920 divided by 421 is 2 with a remainder of 78.
Use 2 as the next digit of our solution. 
Result so far: 208734.9857482
Deduct 842 from 920 and we're left with 78.
Since there are no more digits in the dividend, we add a zero to the remainder making it 780, and continue the process.

Moving on to step 16:
When dividing 780 by 421, we get 1 with a remainder of 359.
Write down 1 as next digit of the result. 
Result so far: 208734.98574821
If we subtract 421 from 780, we get 359.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3590, and continue the process.

After the division, we end up with 208734.98574821 and a remainder of 3.59e-07.