The answer is letter U.
U is the second letter of the word QUARTER which means one fourth (1/4).
Below are some letter riddles with answers (courtesy of letter.riddles.tel):
Why is the letter D like a sailor? Answer: Because it follows the C.
How do you get pies to work for the government? Answer: You add the letter S and get spies.
What is the correct way to file an axe? Answer: Under the letter A.
Why do your uncles, aunts, and cousins depend on you? Answer: Without U, they would not exist.
Why is the letter D so aggravating? Answer: Because it makes Ma maD.
What can turn a lad into a lady? Answer: The letter Y.
Why should dieters avoid the letter C? Answer: Because it makes fat a faCt.
Why does Lucy like the letter K? Answer: It makes Lucy lucKy.
What letter is most useful to a deaf woman? Answer: The letter A can make 'her' 'hear'.
What ends with E and begins with P and has a thousand letters? Answer: Post office.
Hard riddles are a true test of your mental power and comprehension. Try to solve these challenging and puzzling brain teasers from RiddleMinistry.com.