Mark your code as a spoiler.

Look at this line of code: (p0*(percent/100)). The value that this code returns will contain remainders, in decimals. However, this is not possible as we are talking about population here so there can not be "fractional remainders" of people.

For example, if p0 = 1500 and percent = 2.5, then (p0*(percent/100)) == 37.5 people. Which is incorrect because it is not possible to have 37 and 'a half' humans.

Your code is wrong because you think that fractional parts of people give birth which is wrong.