172138 divided by 45 
We want to figure out the number of times 172138 can be divided by 45.

Step 1:
45 goes into 1 0 times with a remainder of 1.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
Deduct 0 from 1 and we're left with 1.
Include the next digit (7) from the dividend after 1, then repeat: 17 / 45

Advancing to step 2:
When dividing 17 by 45, we get 0 with a remainder of 17.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we take 0 away from 17, we end up with 17.
Take the next digit (2) from the dividend and append it to 17, then repeat: 172 / 45

Step 3:
45 can be fit into 172 3 times, resulting in a remainder of 37.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
If we take 135 away from 172, we end up with 37.
Grab the next digit (1) from the dividend, add it to 37, then carry on: 371 / 45

Moving on to step 4:
When dividing 371 by 45, we get 8 with a remainder of 11.
The number 8 becomes the next digit in our result. 
Result so far: 38.0
Subtracting 360 from 371 leaves us with 11.
Bring next digit (3) of the dividend behind the 11 and repeat the process: 113 / 45

Moving on to step 5:
45 goes into 113 2 times with a remainder of 23.
Write down 2 as next digit of the result. 
Result so far: 382.0
Subtract 90 from 113 to get 23.
Include the next digit (8) from the dividend after 23, then repeat: 238 / 45

On to step 6:
The number 45 fits into 238 5 times, leaving a remainder of 13.
The next digit of our result is 5. 
Result so far: 3825.0
Deduct 225 from 238 and we're left with 13.
Since there are no more digits in the dividend, we add a zero to the remainder making it 130, and continue the process.

Going ahead to step 7:
The number 45 fits into 130 2 times, leaving a remainder of 40.
Put 2 as the next digit of the answer. 
Result so far: 3825.2
Deduct 90 from 130 and we're left with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

Going ahead to step 8:
When dividing 400 by 45, we get 8 with a remainder of 40.
Record the quotient 8 as the next digit in the result. 
Result so far: 3825.28
Subtracting 360 from 400 leaves us with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

On to step 9:
If we divide 400 by 45, we get 8 and a remainder of 40.
Write down 8 as next digit of the result. 
Result so far: 3825.288
If we take 360 away from 400, we end up with 40.
Since there are no more digits in the dividend, we add a zero to the remainder making it 400, and continue the process.

The final outcome is 3825.288, with a leftover of 0.004.