What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

You are trapped in a room with two doors. One leads to certain death and the other leads to freedom. You don't know which is which.
There are two robots guarding the doors. They will let you choose one door but upon doing so you must go through it.
You can, however, ask one robot one question. The problem is one robot always tells the truth, the other always lies and you don't know which is which.
What is the question you ask?

How many letters are in the alphabet?

Can you write down eight eights so that they add up to one thousand?

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

15 caves are arranged in a circle at the temple of doom. One of these caves has the treasure of gems and wealth. Each day the treasure keepers can move the treasure to an adjacent cave or can keep it in the same cave. Every day two treasure seekers visit the place and have enough time to enter any two caves of their choice.

How do the treasure seekers ensure that they find the treasure in the minimum number of possible days?

What kind of band never plays music?

If six children and two dogs were under an umbrella, how come none of them got wet?

What came first, the chicken or the egg?