Hundred Doves

This is a math riddle often asked in Portugal to kids, specially those who are good at math. There are two versions of the same riggle, but if you can do one, you will most likely be able to do the other - I leave you both, just in case:

A hawk flies by a flock of doves and says:

– Hellow hundred doves.

– We are not an hundred doves – the doves replies – but us, as much as us and a quarter of us together, and you hawk, makes a hundred.

So, how many are the doves in the flock?

In the second version, the doves reply, instead:

We are not one hundred doves, but us, as much as us, half od us, a quarter of us and you, hawk, a hundred would be.

So, can you find out how many doves are in each of the flocks?

And, obviously, solve them using only your head, no pen and papel or electronics.