What number comes next in the series?

5 15 5 18 5 24 14 20 _

How many times do a clock's hands overlap in a day ?

What does this mean?

CCCCCCC

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

A cat, a dog and a monkey were stolen. 3 suspects got caught: Harish, Manoj and Tarun. All we know is each person stole one animal, but we do not know who stole which. Here are the investigation statements. Harish said: Tarun stole the cat. Manoj said: Tarun stole the dog. Tarun said: They both were lying. I did not steal the cat or the dog. Later on, the police found out the man who stole the monkey told a lie. The man who stole the cat told the truth. Can you find out who stole which?

You are given 16 witch hats. The hats are divided in four different colours – red, blue, green and yellow. Every colour has been assigned to four hats. Now each of the hat will be glued with a label of an arithmetic sign – ‘+’, ‘-‘, ‘x’ or ‘/’. But you can label one sign only once on one colour. In such an arrangement, the hats can be uniquely defined by its colour and symbol.

Can you arrange all the 16 hats in a 4x4 grid in a fashion that no two rows and columns have a repetition of colour or sign?
We have arranged four hats in the below picture to assist you.

Can you name some countries which do not have the alphabet 'A' in them?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?