What is next number in the pattern below:

131 517 192 123 ?

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

It can't be seen, can't be felt, can't be heard, and can't be smelt.
It lies behind stars and under hills, And empty holes it fills.
It comes first and follows after, Ends life, and kills laughter.
What is it?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

What do you see in the image below

I left my campsite and hiked south for 3 miles. Then I turned east and hiked for 3 miles. I then turned north and hiked for 3 miles, at which time I came upon a bear inside my tent eating my food! What colour was the bear?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?