What is next number in the pattern below:

131 517 192 123 ?

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

I am a three digit number.
My tens digit is five more than my ones digit.
My hundreds digit is eight less than my tens digit.
What number am I?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

Alex is stranded on an island covered in forest.
One day, when the wind is blowing from the west, lightning strikes the west end of the island and sets fire to the forest. The fire is very violent, burning everything in its path, and without intervention the fire will burn the whole island, killing the man in the process.

There are cliffs around the island, so he cannot jump off.

How can the Alex survive the fire? (There are no buckets or any other means to put out the fire)

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?

I am green and found in the forest and have needles instead of leaves. What am I?
Hint 1: It can be used for Christmas decorations.
Hint 2: I have a strong, scent that is used in air fresheners.

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

What does an Island and the letter T have in common?