If eleven plus two equals one, what does nine plus five equal?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

If an electric train is travelling south, then which way is the smoke going?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

How many letters are in the alphabet?

Count the number of times the letter "F" appears in the following paragraph:

FAY FRIED FIFTY POUNDS OF
SALTED FISH AND THREE POUNDS
OF DRY FENNEL FOR DINNER FOR
FORTY MEMBERS OF HER FATHER'S FAMILY.

Can you name three consecutive days without using the words Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

Why 1729 is a magic number? Answer Logically.