Let's divide 343591 by 3
The aim is to understand the frequency of 3 in 343591.

Advancing to step 1:
3 goes into 3 1 times with a remainder of 0.
Put 1 as the next digit of the answer. 
Result so far: 1.0
If we take 3 away from 3, we end up with 0.
Grab the next digit (4) from the dividend, add it to 0, then carry on: 4 / 3

Moving on to step 2:
3 goes into 4 1 times with a remainder of 1.
Record the quotient 1 as the next digit in the result. 
Result so far: 11.0
Subtract 3 from 4 to get 1.
Grab the next digit (3) from the dividend, add it to 1, then carry on: 13 / 3

Let's proceed to step 3:
When dividing 13 by 3, we get 4 with a remainder of 1.
The number 4 becomes the next digit in our result. 
Result so far: 114.0
The remainder is 1 after subtracting 12 from 13.
Take the next digit (5) from the dividend and append it to 1, then repeat: 15 / 3

On to step 4:
15 divided by 3 is 5 with a remainder of 0.
Record the quotient 5 as the next digit in the result. 
Result so far: 1145.0
Subtracting 15 from 15 leaves us with 0.
Take the next digit (9) from the dividend and append it to 0, then repeat: 9 / 3

Moving on to step 5:
The number 3 fits into 9 3 times, leaving a remainder of 0.
Record the quotient 3 as the next digit in the result. 
Result so far: 11453.0
Deduct 9 from 9 and we're left with 0.
Append the next digit (1) from the dividend to 0 and continue with: 1 / 3

On to step 6:
3 goes into 1 0 times with a remainder of 1.
Write down 0 as next digit of the result. 
Result so far: 114530.0
If we take 0 away from 1, we end up with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Step 7:
10 divided by 3 is 3 with a remainder of 1.
Put 3 as the next digit of the answer. 
Result so far: 114530.3
If we take 9 away from 10, we end up with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

Advancing to step 8:
The number 3 fits into 10 3 times, leaving a remainder of 1.
Put 3 as the next digit of the answer. 
Result so far: 114530.33
Deduct 9 from 10 and we're left with 1.
Since there are no more digits in the dividend, we add a zero to the remainder making it 10, and continue the process.

The final outcome is 114530.33, with a leftover of 0.001.