1 .He lived to be hundred years old.
2. He lived to be a hundred years old
First of all, I wonder I should put 'a' before hundred or not.
3. I have a story to write.
4. I have a story to write about.
5. I have a house to live.
6. I have a house to live in.
Second, I want to know it is not grammatical to say like 3 and 4.
Thank you so much and have a good weekends.