Does not say how many grandchildren. Say n, integer. So, all received some cookies, x, except Cindy, who received 5 less than the even number:
even number= 96/n, Cindy gets 96/n-5, the rest receive the rest of the cookies:
96 - (96/n-5) = 96*(1-1/n) + 5 = 96*(n-1)/n + 5.
Then each of them (n-1) receive the previous number divided by (n-1) -Cindy is not there:
each of the other grandchildren receives:
96/n + 5/(n-1), and Cindy receives 96/n-5, it just needs to be positive.
So any number 'n' which divides 96 and 'n-1' divides 5 works.
Indeed ONLY n=6, makes 5/(6-1) possible.
So there are 6 grandchildren:
5 receive 17 cookies, and Cindy gets 11.
If it were evenly distributed, all would have got 96/6 = 16 cookies.
Now 5 get one more cookie, and Cindy 5 less.
WOW. Very nice problem!! Gonna share it :)