How can a man go eight days without sleep?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

Count the squares in the matchstick puzzle below?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

Can you replace the question mark with the correct number in the below table sequence?

The chance of Mr John winning the lottery is 10%. All participants lined up and Mr John is 4th in the row. The first three participants lose the lottery.

What is the chance of Mr John now?

Prove that the below maths equation is true.

8 + 8 = 91

Jim has three close friends at his school: Michael, John and Alice. Two of them play football, two play basketball and two play hockey. The friend who does not play hockey does not play basketball as well. The friend who does not play football does not play hockey.

Can you identify which sport/s is played by which person?

How many points are there on the globe where, by walking one mile south, then one mile east and then one mile north, you would reach the place where you started?