Name one eight-letter word with 'kst' in the middle, 'in' the beginning, 'and' at the end.?

A man has a barrel filled with oil that weighs 100 pounds, and then he puts something into it. Now the barrel weighs less than 100 pounds. What did he put in the barrel?

A Scientist was fifty years old in the year 2000 but he was forty years old in the year 2010. How can this be possible?

PS: It has a logical answer.

Find the last number in the series below:

voN luJ yaM raM ---

I have branches, but no fruit, trunk or leaves. What am I?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

You can hear me, but you can't touch or see me.

What am I?

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?

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?