We're dividing 300458 by 21 
We're looking to find how many times 21 goes into 300458.

Going ahead to step 1:
If we divide 3 by 21, we get 0 and a remainder of 3.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Grab the next digit (0) from the dividend, add it to 3, then carry on: 30 / 21

On to step 2:
If we divide 30 by 21, we get 1 and a remainder of 9.
Use 1 as the next digit of our solution. 
Result so far: 1.0
If we take 21 away from 30, we end up with 9.
Bring next digit (0) of the dividend behind the 9 and repeat the process: 90 / 21

On to step 3:
21 goes into 90 4 times with a remainder of 6.
The next digit of our result is 4. 
Result so far: 14.0
The remainder is 6 after subtracting 84 from 90.
Append the next digit (4) from the dividend to 6 and continue with: 64 / 21

Going ahead to step 4:
21 can be fit into 64 3 times, resulting in a remainder of 1.
Write down 3 as next digit of the result. 
Result so far: 143.0
If we take 63 away from 64, we end up with 1.
Fetch the next digit (5) from the dividend, attach it to 1 and continue: 15 / 21

Step 5:
If we divide 15 by 21, we get 0 and a remainder of 15.
The next digit of our result is 0. 
Result so far: 1430.0
The remainder is 15 after subtracting 0 from 15.
Grab the next digit (8) from the dividend, add it to 15, then carry on: 158 / 21

On to step 6:
When dividing 158 by 21, we get 7 with a remainder of 11.
Write down 7 as next digit of the result. 
Result so far: 14307.0
Subtracting 147 from 158 leaves us with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 7:
If we divide 110 by 21, we get 5 and a remainder of 5.
The next digit of our result is 5. 
Result so far: 14307.5
If we subtract 105 from 110, we get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Going ahead to step 8:
When dividing 50 by 21, we get 2 with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 14307.52
Deduct 42 from 50 and we're left with 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

Moving on to step 9:
21 can be fit into 80 3 times, resulting in a remainder of 17.
The next digit of our result is 3. 
Result so far: 14307.523
Subtracting 63 from 80 leaves us with 17.
Since there are no more digits in the dividend, we add a zero to the remainder making it 170, and continue the process.

Advancing to step 10:
21 goes into 170 8 times with a remainder of 2.
Put 8 as the next digit of the answer. 
Result so far: 14307.5238
If we take 168 away from 170, we end up with 2.
Since there are no more digits in the dividend, we add a zero to the remainder making it 20, and continue the process.

On to step 11:
21 can be fit into 20 0 times, resulting in a remainder of 20.
Write down 0 as next digit of the result. 
Result so far: 14307.5238
Subtracting 0 from 20 leaves us with 20.
Since there are no more digits in the dividend, we add a zero to the remainder making it 200, and continue the process.

Step 12:
21 goes into 200 9 times with a remainder of 11.
Use 9 as the next digit of our solution. 
Result so far: 14307.523809
If we take 189 away from 200, we end up with 11.
Since there are no more digits in the dividend, we add a zero to the remainder making it 110, and continue the process.

Step 13:
The number 21 fits into 110 5 times, leaving a remainder of 5.
The next digit of our result is 5. 
Result so far: 14307.5238095
Subtract 105 from 110 to get 5.
Since there are no more digits in the dividend, we add a zero to the remainder making it 50, and continue the process.

Moving on to step 14:
21 goes into 50 2 times with a remainder of 8.
Record the quotient 2 as the next digit in the result. 
Result so far: 14307.52380952
If we subtract 42 from 50, we get 8.
Since there are no more digits in the dividend, we add a zero to the remainder making it 80, and continue the process.

The final result is 14307.52380952 with a remainder of 8e-09.