Find the next number in the sequence

1, 2, 6, 21, 88, __?

Can you count the number of triangles inside a triangle?

2, 3, 5, 9, 17, _ What is the next number in the sequence?

Why 1729 is a magic number? Answer Logically.

Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

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

How many people must be gathered together in a room, before you can be certain that there is a greater than 50/50 chance that at least two of them have the same birthday?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?