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

A patient was diagnosed with some ailment. He was given five different tablets to take at night at an interval of 15 minutes.

How long will it take the patient to consume all the five tablets?

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

You knock a Table over in the library, and suddenly 20 eyes are looking at you.

What does this rebus mean?

O
N
C
E
TIME

In a concert, Christina is performing a dance show with her group.
At 10:00, she and her crew were dancing in an absolutely straight line. At that time Christina was standing in 4th position from both the front and back end of the row.

What was the size of her crew?

Before Mount Everest was discovered, what was the highest mountain in the world?

Your last good ping-pong ball fell into a narrow metal pipe embedded one foot deep in concrete.
How can you get it out undamaged, if all the tools you have are your tennis paddle, shoe laces, and plastic water bottle, which does not fit into the pipe?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

Can you move 2 matchsticks to form four equal sized squares.