One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

What number do you get when you multiply all of the numbers on a telephone's number pad?

What is black when you buy it, red when you use it, and gray when you throw it away?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

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?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Can you write down eight eights so that they add up to one thousand?

Can you complete the sequence?

192, 021, 222, 324, 252, 627, 2__, 9__?

If you read clockwise, you can form a word by inserting three missing letters in the picture given below. Can you do it?