How many sides does a circle have?

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

Solve the rebus riddle in the picture below.

You can hear me, but you can't touch or see me.

What am I?

Two friends were betting. One said to the other, "The coin will be flipped twenty times and each time the coin lands on the head, I will give you $2 and each time it lands on the tale, you will give me $3." After flipping the coin twenty times not a single penny was exchanged among them.

How many times did the coin land on heads?

Nine marbles are arranged in the image below. Can you slide two marbles to form a square?

Which five letter word can be added at the end of below word to form a
valid word?

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Three playing cards in a row. Can you name them with these clues? There is a two to the right of a king. A diamond will be found to the left of a spade. An ace is to the left of a heart. A heart is to the left of a spade. Now, identify all three cards.

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle:

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?