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

What does it mean?

Queen Elizabeth organised a royal party.

To Avoid uninvited guest royal family set a password.
Jack (an uninvited person) plan to enter the party. He stand nearby the door.

First guest comes, the security person said 'twelve' and guest replied with six.
Second guest comes , the security person said 'six' and guest replied with 'three'.

Jack thought is enough and he walked to the entry point. The security person said 'eight' , Jack replied smilingly 'four'.
He was immediately thrown out of the party. why ?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

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

A father's child, a mother's child, yet no one's son.

Who am I?