Can you count the number of quadrilaterals in the picture below?

What always comes into a house through the keyhole?

Different lights make me strange by changing me into different sizes. What am I?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Ten coins have been arranged as you can see in the given picture. In this arrangement, a triangle is formed pointing upwards. You have to invert the position of the triangle and make it point downwards while changing the position of 3 coins only. Can you do it?

I have nine bottles of wine and one of the nine bottles is poisoned.
I need to find the poisoned bottle with two facts
(1) Poison is deadly, only a sip will cost death
(2) I have two mice to do so.

How should I do it?

Wednesday, Steve and Pam go to a restaurant to eat lunch. After eating lunch, they pay the bill. But Steve and Pam do not pay the bill. So…who does?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

10+10 and 11+11 can give you the same answer.

Explain how?

2, 3, 5, 9, 17, _ What is the next number in the sequence?