Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Find the value of "?" in the ball picture Riddle below:

There are seven sisters in a house in a village where there is no electricity or any gadget.

Sister-1: Reading Novel
Sister-2: Cooking
Sister-3: Playing Chess
Sister-4: Playing Sudoku
Sister-5: Washing clothes
Sister-6: Gardening

what is Sister-7 doing ?

A non-stop marathon is the shared favourite sport of three brothers.

*The oldest one is fat and short and trudges slowly on.
*The middle brother's tall and slim and keeps a steady pace.
*The youngest runs just like the wind, speeding through the race.

"He is young in years, we let him run!" the other two brothers explained, "'because though he is surely number one, he is second, in a way." Why is it?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

The husband and wife were jogging in the morning. To match every two steps of the husband, the wife required three steps. If Both of them start with the here right foot. After how many steps do their left foot be together?

I look at you, you look at me, I raise my right, you raise your left. What am I?

There's one "sport" in which neither the spectators nor the participants know the score or the leader until the contest ends.

What is it?

I have no life, but I can die. What am I?

I am an odd number. Take away a letter and I become even. What number am I?