Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Christina, Allison and Lena are 3 daughters of John a well-known Mathematician, When I asked John the age of their daughters. He replied "The current age of her daughters is prime. Also, the difference between their ages is also prime."

How old are the daughters?

What has no start, end, or centre?

Why are televisions attracted to people?

Which Travels Faster? Solve below famous picture riddle:

There are forty elephants and they have forty-fore heads. How can this be possible?

Why do you find that most of the buildings are deprived of the 13th floor?

A Child was born in Lahore, Pakistan.

Still child is not a Pakistani citizen.why ?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

Can you convert the number zero(0) into a positive number using just one mathematical operator ?