Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

I never was there, I am always to be.
You have never ever seen me, not ever you will.
Yet I am the confidence of everyone.

Who Am I?

Katniss and Peeta are liars. They both lie on some specific days.

Katniss lies on Fridays, Saturdays and Sundays. She speaks the truth on all other days.

Peeta lies on Tuesdays, Wednesdays and Thursdays. He speaks the truth on all other days.

Can you tell that one day of the week when both of them will say "Tomorrow, I will lie."?

Guess the hidden movie name?

I can be made.
I can be cracked.
I can be told.
I can be played.

Who am I?

A few friends are enjoying their sea voyage in a boat full of apples. On the way, they felt hungry and thus decided to eat the apples. Together, they ate two dozen of apples. When they have eaten the apples, will there be any change in the water level?

What question can you never answer yes to?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

You have a basket containing ten apples. You have ten friends, who each desire an apple. You give each of your friends one apple.
Now all your friends have one apple each, yet there is an apple remaining in the basket.
How?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?