What is common among 11, 69, and 88?

What is the coolest letter in the alphabet?

Pronounced as 1 letter, And written with 3, 2 letters there are, and 2 only in me. I’m double, I’m single, I’m black blue and grey, I’m read from both ends, and the same either way. What am I?

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

Can you find the thief by just looking at the picture below?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

Can you find out the missing number in the grid?

Why is Saturday stronger than Monday?

Replace the question mark with the number below given a simple math problem.