Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

What is next number in the pattern below:

131 517 192 123 ?

If,

Akriti = 631
Levis = 521
Sroti = 521
Aneel = 533
Then,
Sunil =?

What makes this number unique: 8,549,176,320?

The host of a game show, offers the guest a choice of three doors. Behind one is a expensive car, but behind the other two are goats.
After you have chosen one door, he reveals one of the other two doors behind which is a goat (he wouldn't reveal a car).

Now he gives you the chance to switch to the other unrevealed door or stay at your initial choice. You will then get what is behind that door.

You cannot hear the goats from behind the doors, or in any way know which door has the prize.

Should you stay, or switch, or doesn't it matter?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

The following sentence is false. The preceding sentence is true.
Are these two sentences true or false?

A tree doubled in height each year until it reached its maximum height over the course of ten years. How many years did it take for the tree to reach half its maximum height?

Which word is least like the others? Third, fourth, fifth, sixth, seventh, eighth, ninth?