What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

I am a five-letter word and comprises two different vowels and three same consonants. I am so strong that I can spoil your entire work.

Can you find out who am I?

10 people came into a hotel with 9 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the tenth guest to wait for a little with the first guest in room number 1. So in the first room, there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, ..., and the ninth guest to room number 8. Then he returned to room number 1 and took the tenth guest to room number 9, still vacant.
How can everybody have his own room?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

What is the next number in the series?

15 29 56 108 208 ?

A few friends are enjoying their sea voyage in a boat full of apples. On the way, they felt hungry and thus decided to eat the apples. Together, they ate two dozen of apples. When they have eaten the apples, will there be any change in the water level?

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

What Does this text mean:

important=important