They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

Two guards were on duty outside a barracks. One faced up the road to watch for anyone approaching from the North. The other looked down the road to see if anyone approached from the South. Suddenly one of them said to the other, "Why are you smiling?"

How did he know his companion was smiling?

Below is the sum of symbols in each row and column in the figure. Analyzing the figure, can you find out the value of the symbols?

How is the moon similar to a dollar?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

How can you make number one disappear by adding something to it?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

What goes up but never comes down?