Find the next number in the series below

21 32 54 87 131 ?

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

It comprises roots which nobody sees,
Much taller than those trees,
Up and up it goes,
Still it never grows?

A man walked into a pub and went straight towards the Barman. He asked for a dirty martini from the Barman. The Barman thought something and then pulled out a pistol from his drawer and aimed it directly at the man. Why did he do that?

What is both possible and impossible at the same time?

I have branches, but no fruit, trunk or leaves. What am I?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

If you’ve got me, you want to share me; if you share me, you haven’t kept me. What am I?