ok, im stumped.
===
In a remote island somewhere off the coast of Brazil (I'm Brazilian)
there lives a very peculiar species of large non-flying birds, whose
colorful tail feathers are extremely valuable in the collector's
black market. One night (call it the night of day 0), a poacher
manages to sneak in amidst a flock of these birds, while they're
asleep, and snaps off a number of tail feathers, one feather per bird.
When he left, however, he accidentally dropped one feather but,
fearing being discovered by the native inhabitants - who worship the
birds and would sacrifice him to them - he never took it back and,
instead, rushed away to his boat and left the island.
Your task is to figure out how many feathers the poacher snapped off,
knowing the following facts:
- the birds all see each other completely;
- all the birds also see the feather left on the ground by the poacher;
- the birds never communicate in any way with each other (except
during mating season, but the poacher knew better than to sneak in
during mating season...);
- the birds are too large and fat to be able to look at their own
behinds and find out if they have had their tails snapped off, and no
pain nor any other sign exists that could indicate the absence or
presence of a tail, with the exception to be explained below;
- the birds think logically;
- whenever a bird can *logically* deduce, without any shred of doubt,
and only then, that its own tail has been cut, it dies. But not
immediately, mind you. No. The poor bird goes to sleep that night, as
usual, but doesn't wake up in the next morning;
- all birds can tell when another bird is dead;
- on the morning of the 27th day, there are still living birds
without their tails, but on the 28th day, all birds who have had
their tails cut are dead.
Once again, how many feathers have been taken?
--
In a remote island somewhere off the coast of Brazil (I'm Brazilian)
there lives a very peculiar species of large non-flying birds, whose
colorful tail feathers are extremely valuable in the collector's
black market. One night (call it the night of day 0), a poacher
manages to sneak in amidst a flock of these birds, while they're
asleep, and snaps off a number of tail feathers, one feather per bird.
When he left, however, he accidentally dropped one feather but,
fearing being discovered by the native inhabitants - who worship the
birds and would sacrifice him to them - he never took it back and,
instead, rushed away to his boat and left the island.
Your task is to figure out how many feathers the poacher snapped off,
knowing the following facts:
- the birds all see each other completely;
- all the birds also see the feather left on the ground by the poacher;
- the birds never communicate in any way with each other (except
during mating season, but the poacher knew better than to sneak in
during mating season...);
- the birds are too large and fat to be able to look at their own
behinds and find out if they have had their tails snapped off, and no
pain nor any other sign exists that could indicate the absence or
presence of a tail, with the exception to be explained below;
- the birds think logically;
- whenever a bird can *logically* deduce, without any shred of doubt,
and only then, that its own tail has been cut, it dies. But not
immediately, mind you. No. The poor bird goes to sleep that night, as
usual, but doesn't wake up in the next morning;
- all birds can tell when another bird is dead;
- on the morning of the 27th day, there are still living birds
without their tails, but on the 28th day, all birds who have had
their tails cut are dead.
Once again, how many feathers have been taken?
--
