How many sides does a circle have?

If eleven plus two equals one, what does nine plus five equal?

How many letters are in the alphabet?

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

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

I get hot but I never sweat,
I cook food but I am not a chef,
I have a door but you can't enter me,
I have a light but I am not a lamp.
Who am I?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

What is the Surname of Barbie Doll?