Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

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

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

What do you get if you add 2 to 100 four times?

A man hijacks an aeroplane transporting both passengers(8 of them) and valuable cargo. After taking the cargo, the man demands nine parachutes, puts one of them on, and jumps, leaving the other eight behind. Why did he want eight?

You are provided with a grid (as shown in the picture). Can you fill the squares with numbers 1-8 in a manner that none of the two consecutive numbers are placed next to each other in any direction (vertically, horizontally or diagonally?)

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

By what process could you make a 'Tea-Table' into food?

A man dies of old age on his 25 birthday. How is this possible?

what's the probability of getting a king or a queen from a pack of 52 cards?