Calculating percentage in a table is giving correct and wrong answers with the same query

I have a table with year, area codes and each area code has 5 categories of age groups with people count as below.

I need to calculate percentage of persons for each group out of total persons per areacode, the result I need is:

But the result I'm getting is bizarre, it is partially giving correct answers and also wrong answers. See below result.

Any percentage that is other than 0 or 100, is resulting in 0% To test the total_sum column, I added the test column where the total is 0 give 0, else 1. And that works perfectly fine.

I'm using the following code:

select 
    table.fid, 
    table.year, 
    table.areacode,
    table.agegroup,
    table.persons,
    totals.total_sum,
    case
        when totals.total_sum = 0 then 0
        else 1
    end as test,
    case
        when totals.total_sum = 0 then 0
        else ((table.persons)/totals.total_sum)*100.0
    end as percent
from abc.table
join (
    select
        table.year,
        table.areacode,
        sum(table.persons) as total_sum
    from abc.table
    group by table.areacode, table.year) as totals
on table.areacode = totals.areacode and table.year=totals.year
group by table.areacode, table.fid, table.year, table.agegroup, totals.total_sum
order by totals.total_sum

I tried finding anything related to this kind of error, but unfortunately, I didn't find anything (Maybe, I'm using the wrong keywords).

Does anyone know why is this happening? I'd really appreciate it.

Integer division discards remainders. You need to change one integer into a float before the division is done. Just move the constant upfront and inside the parentheses

(100.0*table.persons/totals.total_sum)