Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

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?

John can fit six large chocolate boxes or nine small chocolate boxes into a carton. How many cartons will he require to put sixty-six chocolate boxes into?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

An artist while painting a scenic beauty, decides to paint three layers of blue colour on the sky.

Which layer will go on the first?

By what process could you make a 'Tea-Table' into food?

Can you find out which options fits best with the missing column?

Count the number of triangles in the below picture?

What Deficiency does the below rebus represent?

VIT_MIN

What goes up but never comes down?