logicYou overhear a man talking to a clerk in a hardware store. The clerk says "One will cost you 12 cents, ten will cost your 24 cents, and one hundred will cost you 36 cents."
What is the man buying?

The man is buying physical numbers to nail to the front of his house. Each number costs 12 cents, and so "1" will cost 12 cents, "10" will cost 24 cents, and "100" will cost 36 cents.

## Similar riddles

See also best riddles or new riddles.

logicTwo Japanese people who have never seen each other meet at the New York Japanese Embassy. They decide to have drinks together at a nearby bar. One of them is the father of the other one's son. How is this possible?

The Japanese are husband and wife and both blind since birth.

logic Once upon a time there was a dad and 3 kids. When the kids were adults, the dad was old and Death came to take the dad. The first son, who became a lawyer, begged Death to let the dad live a few more years. Death agreed. When Death came back, the second son, who became a doctor begged Death to let his father live a few more days. Death agreed. When Death came back the third son, who became a priest begged Death to let the dad live till that candle wick burned out and he pointed to a candle. Death agreed. The third son knew Death wouldn't come back, and he didn't. Why not?

The third son went over and blew out the candle after Death left because the son said "till the candle wick burns out", not "till the candle burns out".

cleanlogicshortWhat did the boy bird say to the girl bird on Valentine's Day?

Let me call you Tweet heart.

logicmathprobabilityYou are on a gameshow and the host shows you three doors. Behind one door is a suitcase with $1 million in it, and behind the other two doors are sacks of coal. The host tells you to choose a door, and that the prize behind that door will be yours to keep.
You point to one of the three doors. The host says, "Before we open the door you pointed to, I am going to open one of the other doors." He points to one of the other doors, and it swings open, revealing a sack of coal behind it.
"Now I will give you a choice," the host tells you. "You can either stick with the door you originally chose, or you can choose to switch to the other unopened door."
Should you switch doors, stick with your original choice, or does it not matter?

You should switch doors.
There are 3 possibilities for the first door you picked:
You picked the first wrong door - so if you switch, you win
You picked the other wrong door - again, if you switch, you win
You picked the correct door - if you switch, you lose
Each of these cases are equally likely. So if you switch, there is a 2/3 chance that you will win (because there is a 2/3 chance that you are in one of the first two cases listed above), and a 1/3 chance you'll lose. So switching is a good idea.
Another way to look at this is to imagine that you're on a similar game show, except with 100 doors. 99 of those doors have coal behind them, 1 has the money. The host tells you to pick a door, and you point to one, knowing almost certainly that you did not pick the correct one (there's only a 1 in 100 chance). Then the host opens 98 other doors, leave only the door you picked and one other door closed. We know that the host was forced to leave the door with money behind it closed, so it is almost definitely the door we did not pick initially, and we would be wise to switch.

logicmathTwo words are anagrams if and only if they contain the exact same letters with the exact same frequency (for example, "name" and "mean" are anagrams, but "red" and "deer" are not).
Given two strings S1 and S2, which each only contain the lowercase letters a through z, write a program to determine if S1 and S2 are anagrams. The program must have a running time of O(n + m), where n and m are the lengths of S1 and S2, respectively, and it must have O(1) (constant) space usage.

First create an array A of length 26, representing the counts of each letter of the alphabet, with each value initialized to 0. Iterate through each character in S1 and add 1 to the corresponding entry in A. Once this iteration is complete, A will contain the counts for the letters in S1. Then, iterate through each character in S2, and subtract 1 from each corresponding entry in A. Now, if the each entry in A is 0, then S1 and S2 are anagrams; otherwise, S1 and S2 aren't anagrams.
Here is pseudocode for the procedure that was described:
def areAnagrams(S1, S2)
A = new Array(26)
A.initializeValues(0)
for each character in S1
arrayIndex = mapCharacterToNumber(character) //maps "a" to 0, "b" to 1, "c" to 2, etc...
A[arrayIndex] += 1
end
for each character in S2
arrayIndex = mapCharacterToNumber(character)
A[arrayIndex] -= 1
end
for (i = 0; i < 26; i++)
if A[i] != 0
return false
end
end
return true
end

logic If you had one match and entered a room in which there were a kerosene lamp, an oil burner, and a wood burning stove, which would you light first?

The match.

logicmysteryscaryA man is found murdered on a Sunday morning. His wife calls the police, who question the wife and the staff, and are given the following alibis: the wife says she was sleeping, the butler was cleaning the closet, the gardener was picking vegetables, the maid was getting the mail, and the cook was preparing breakfast.
Immediately, the police arrest the murdered. Who did it and how did the police know?

The maid. There is no mail on Sundays.

logicmysteryscaryThe Smith family is a very wealthy family that lives in a big, circular home. One morning, Mr. Smith woke up and found his gardener's body. He knew it was one of his employees who had killed him. So he asked them what they were doing in the morning and he got these replies.
Driver: "I was outside washing the car."
Maid: "I was dusting the corners of the house."
Cook: "I was starting to make lunch for later."
From the replies he knew who the killer was. Can you guess who it was?

The maid, because they lived in a circular house and she was apparently "dusting the corners" of the house at the time of the murder - the house is round, therefore it has no corners.

logicAllan, Bertrand, and Cecil were caught stealing so the king sent them to the dungeon.
But the king decided to give them a chance.
He mad them stand in a line and put hats on their heads.
He told them that if they answer a riddle, they could go free.
Here is the riddle: "Each of you has a hat on your head. You do not know the color of the hat on your own head. If one of you can guess the color of the hat on your head, I will let you free. But before you answer you must keep standing in this line. You cannot turn around. Here are my only hints: there are only black and white hats. At least one hat is black. At least one hat is white."
Allan couldn't see any hats.
Bertrand could see Allan's hat but not his own.
Cecil could see Bertrand's hat and Allan's hat, but not his own.
After a minute nobody had solved the riddle. But then a short while later, one of them solved the riddle. Who was is and how did he know?

Bertrand knew the answer because Cecil didn't say anything after one minute. If Bertrand and Allan's hats were both the same color, then Cecil would know what color his hat was. But Cecil didn't know. So Bertrand knew that Allan's hat was a different color than his. Since Allan's hat was black, Betrand knew his hat was white.

logicAn iron horse with a flaxen tail.
The faster the horse runs,
the shorter his tail becomes.
What is it?

A needle and thread.