We look at the division of 42121509 by 257 
We're looking to find how many times 257 goes into 42121509.

Going ahead to step 1:
The number 257 fits into 4 0 times, leaving a remainder of 4.
Write down 0 as next digit of the result. 
Result so far: 0.0
The remainder is 4 after subtracting 0 from 4.
Fetch the next digit (2) from the dividend, attach it to 4 and continue: 42 / 257

Step 2:
If we divide 42 by 257, we get 0 and a remainder of 42.
Write down 0 as next digit of the result. 
Result so far: 0.0
Subtracting 0 from 42 leaves us with 42.
Fetch the next digit (1) from the dividend, attach it to 42 and continue: 421 / 257

Step 3:
When dividing 421 by 257, we get 1 with a remainder of 164.
Write down 1 as next digit of the result. 
Result so far: 1.0
The remainder is 164 after subtracting 257 from 421.
Take the next digit (2) from the dividend and append it to 164, then repeat: 1642 / 257

Let's proceed to step 4:
If we divide 1642 by 257, we get 6 and a remainder of 100.
The number 6 becomes the next digit in our result. 
Result so far: 16.0
Deduct 1542 from 1642 and we're left with 100.
Append the next digit (1) from the dividend to 100 and continue with: 1001 / 257

Step 5:
The number 257 fits into 1001 3 times, leaving a remainder of 230.
The next digit of our result is 3. 
Result so far: 163.0
Subtract 771 from 1001 to get 230.
Fetch the next digit (5) from the dividend, attach it to 230 and continue: 2305 / 257

Let's proceed to step 6:
If we divide 2305 by 257, we get 8 and a remainder of 249.
Write down 8 as next digit of the result. 
Result so far: 1638.0
If we subtract 2056 from 2305, we get 249.
Fetch the next digit (0) from the dividend, attach it to 249 and continue: 2490 / 257

On to step 7:
2490 divided by 257 is 9 with a remainder of 177.
The next digit of our result is 9. 
Result so far: 16389.0
If we subtract 2313 from 2490, we get 177.
Append the next digit (9) from the dividend to 177 and continue with: 1779 / 257

Advancing to step 8:
When dividing 1779 by 257, we get 6 with a remainder of 237.
The next digit of our result is 6. 
Result so far: 163896.0
If we subtract 1542 from 1779, we get 237.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2370, and continue the process.

Advancing to step 9:
If we divide 2370 by 257, we get 9 and a remainder of 57.
Put 9 as the next digit of the answer. 
Result so far: 163896.9
If we subtract 2313 from 2370, we get 57.
Since there are no more digits in the dividend, we add a zero to the remainder making it 570, and continue the process.

Advancing to step 10:
If we divide 570 by 257, we get 2 and a remainder of 56.
Use 2 as the next digit of our solution. 
Result so far: 163896.92
If we take 514 away from 570, we end up with 56.
Since there are no more digits in the dividend, we add a zero to the remainder making it 560, and continue the process.

Going ahead to step 11:
560 divided by 257 is 2 with a remainder of 46.
Put 2 as the next digit of the answer. 
Result so far: 163896.922
Subtracting 514 from 560 leaves us with 46.
Since there are no more digits in the dividend, we add a zero to the remainder making it 460, and continue the process.

In conclusion, the division gives 163896.922 with a balance of 0.0046.