Answer:
When Margaret is gonna divide 829 by 4, she first needs to divide 8 by 4, which is 2. Then, she has to divide 2 by 4 which is not possible in that case, because 2 is less than 4, to solve that situation, she has to add a zero in the tens to use the next digit and continue with the division.
So, basically, the reason of adding a zero is because 2 is less than 4, and the division has to be a higher number divided by a lower number.
The image attached show the long division.
