Logic Riddles

Question: Swallowing one is fine.
Swallowing two together is fine.
But Swallow them separately and all shall fall.

What are they?

Question: What is yours, but only others can use it?

Question: No matter how terrible things get for the people of the Arctic, they will not eat a penguin.

Why not?

Question: I am a nice word composed of five letters, but the Romans would call me a numbers.

What am I?

Question: Five pirates are parting ways after finding a treasure of 100 pieces of gold. The pirates decide to split it based on a vote. Each pirate, from oldest to youngest, gets to propose a plan on how to split the gold.

If at least 50 percent of the other remaining pirates agree on the plan, that is how they will split the gold. If less than 50 percent of the pirates agree, the pirate who came up with the plan will be thrown overboard. Each pirate is smart, greedy, and wants to throw as many others overboard as possible without reducing the amount of gold they get.

What plan can the first (oldest) pirate propose to live and get as much gold as possible?