Here's my solution...
Day 0 = The Pandavas won a hen = 1
Hens born on Day 1 = 1 hen gave birth to 7 children = 7
Hens born on Day 2 = 7 hen in turn gave birth to 7 children each = 49
Hens born on Day 3 = 49 in turn gave birth to 7 children each = 343
Hens born on Day 4 = 343 in turn gave birth to 7 children each = 2401
.....
This goes on for 365 days.
At the end of 365 days, pandavas (5 brothers) sum up all the available hens and then divide hens among themselves.
We have to observe a pattern here. Unit's digit of number of hens born on a given day will in the pattern of 7,9,3,1,7,9,3,1,... Observe that there are 4 distinct numbers here: 7,9,3 and 1
So if we divide 365 by 4 we get 1 as reminder (4*91 = 364).
So when we add up hens born on each of the 365 days, the units digit of the sum will be 92 times 7(because of the reminder 1 we get when we divide 365 by 4), 91 times 9, 91 times 3 and 91 times 1.
92*7 = 644
91*9 = 819
91*3 = 273
91*1 = 91
to this, we also have to add the mother hen who started the whole population blast.
So units digit of number of hens available to pandavas to divide among themselves is the units digit of 1828 [644 + 819+ 273+ 91 + 1 (mother hen) = 1828]
The number of hens available to pandavas to divide among themselves will be something like xxxxxxxxxxx8. Now if we divide xxxxxxxxxxx8 by 5, the reminder is going to be 3.
So I feel the answer should be 3.
Let me know if I am doing something wrong.