Handel has been killed and Beethoven is on the case. He has interviewed the four suspects and their statements are shown below. Each suspect has said two sentences. One sentence of each suspect is a lie and one sentence is the truth. Help Beethoven figure out who the killer is.
Joplin: I did not kill Handel. Either Grieg is the killer or none of us is.
Grieg: I did not kill Handel. Gershwin is the killer.
Strauss: I did not kill Handel. Grieg is lying when he says Gershwin is the killer.
Gershwin: I did not kill Handel. If Joplin did not kill him, then Grieg did.
Who is the killer?

Strauss is the one who killed Handel. You need to take turns assuming someone is the killer; that means everyone's second sentence is a lie. If Joplin was the killer, Grieg's lie mixed with Strauss' counteracts the other. If Grieg was the killer, Gershwin would need to be a killer too. If Gershwin was the killer, Gershwin would need to be a killer too. If Gershwin was the killer, Grieg and Strauss counter each other again, but with Strauss, everything would fit in.

In a one storey brown house, there was a brown person with a brown computer, brown telephone, and brown chair. He also had a brown cat and a brown fish – Just about everything was brown – What colour was the stairs?

As it was a one-storey house – there were no stairs.

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

Push the cork into the bottle and shake the coin out.

I’m at the beginning of the end
and the start of eternity,
at the end of time and space,
in the middle of yesterday
but nowhere in tomorrow.
What am I?

Elmer Johnson went to the hardware store to make a purchase for his house.
He asked the store clerk, "How much will one cost?"
The clerk thought for a moment and said, "Three dollars."
Elmer Johnson, who looked a little puzzled said, "Well then, how much will twelve cost?"
"Six dollars," replied the clerk.
Elmer Johnson scratched his head and said, "If I were to purchase two hundred, how much would that cost?"
"That," said the clerk, "will cost you nine dollars." What was Elmer Johnson buying?

If a farmer has 5 haystacks in one field and 4 haystacks in the other field, how many haystacks would he have if he combined them all in the center field?

One. If he combines all of his haystacks, they all become one big stack.

Samuel was out for a walk when it started to rain. He did not have an umbrella and he wasn't wearing a hat. His clothes were soaked, yet not a single hair on his head got wet. How could this happen?

Consider the following explanation for why 1=2:
1. Start out Let y = x
2. Multiply through by x xy = x2
3. Subtract y2 from each side xy - y2 = x2 - y2
4. Factor each side y(x-y) = (x+y)(x-y)
5. Divide both sides by (x-y) y = x+y
6. Divide both sides by y y/y = x/y + y/y
7. And so... 1 = x/y + 1
8. Since x=y, x/y = 1 1 = 1 + 1
8. And so... 1 = 2
How is this possible?

Step 5 is invalid, because we are dividing by (x-y), and since x=y, we are thus dividing by 0. This is an invalid mathematical operation (division by 0), and so by not followinng basic mathematical rules, we are able to get strange results like these.

At a local bar, three friends, Mr. Green, Mr. Red and Mr. Blue, were having a drink. One man was wearing a red suit; one a green suit; and the other a blue suit.
"Have you noticed," said the man in the blue suit, "that although our suits have colors corresponding to our names, not one of us is wearing a suit that matches our own names?"
Mr. Red looked at the other two and said, "You're absolutely correct."
What color suit is each man wearing?

Since none of the men are wearing the color of suit that corresponds to their names, and Mr. Red was replying to the man in the blue suit, it had to be Mr. Green to whom he replied. We then know that Mr. Green is wearing a blue suit. Therefore, Mr. Red is wearing a green suit and Mr. Blue is wearing a red suit.