Answer:
11 1/5 feet!
Explanation:
He needs a total of 27 9/10 feet! 11 1/2 + 5 1/5 is 16 7/10 feet! If we need 27 9/10 feet, we subtract 16 7/10 ft from 27 9/10 ft to get 11 2/10, which we can reduce 2/10 to be 1/5.
So, he needs 11 1/5 feet of wood more to build the doghouse for his new puppy!