Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

One is to three as three is to five and five is to four and four is the magic number.
What is the pattern?

How can you write nineteen in a manner that if we take out one, it becomes twenty?

You know three triplets: Frank John and Wayne (need to return your money). Frank always tells the truth while John and Wayne always lie. You meet one of them on the road and can ask him a three-word question.
Which question, will you ask?

In a family supper, a grandfather, a grandmother, two fathers, two mothers, four children, three grandchildren, one brother, two sisters, two sons, two daughters, one daughter-in-law, and one mother-in-law need to sit at a table.

There are only seven chairs available at the place. How many more chairs do they have to borrow so that everyone can sit down together for the suppers if everybody requires a separate chair?

What does this simple rebus mean?

There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

Which word does the below Plexor means ?

What demands an answer, but asks no questions

10+10 and 11+11 can give you the same answer.

Explain how?