Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

In a jungle where there are no street lights or any other artificial source of lights, I notice a black snake crossing the road.
How did I get sight of the snake?

How many times in a given day, minutes and hour clock comes in a straight line ?

What kind of tree can you carry in your hand?

What is full of holes but still holds water?

On a magical land of Mexico , all the animal in the land are rational.

There are 10 tigers and one goat.
Tiger can eat goat but since it's a magical land , the tiger who eats the goat , turns into goat and then can be eaten by the remaining tiger(s).

If we leave them for some time then how many goat and tiger will be there , when we come back ?

Which is faster, Heat or Cold ? Explain.

How many Watermelons are there in the below picture?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?