What is the centre of gravity?

I cannot talk, but I always reply when spoken to. What am I?

The more you take me, the more you leave me behind.
Who Am I?

While going to your grandmother's house, you counted Twenty houses on the right side. While returning back to your home, you counted Twenty houses on the left side.

How many houses are there between your home and your grandmother's home?

What word is represented by this rebus?

what does the below rebus mean?

Can you replace the question mark with the correct number?

I am white when I am dirty, and black when I am clean. What am I?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

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