What goes up and down but doesn't move?

You use me from you head to toe, the more I work the thinner I grow. What am I?

Before Mount Everest was discovered what was the tallest land mountain?

What increases, as you take away from it?

You have 15 marbles and a balancing scale. One marble is lighter than the others. Your teacher tells your class that the person who is able to find the lighter one in the least amount of tries wins 2 million dollars. What is the least amount of times you could use the scale to determine which one is the light one?

Two fathers and two sons go fishing. Each one catches a fish. Yet, they only came home with 3 fish. Why?

Jack left home on a run. First, runs straight, takes a sharp left and keeps running. Does the same thing again and ends back at home. There was two men waiting for him. Who are they?

I shave every day, yet my beard doesn't get shorter. Who am I?

I turn around once and what is out will not get in. I turn around again and what is in will not get out. What am I?

Three doctors say that Robert is their brother. But Robert says he has no brothers. Who is lying?