What word begins and ends with an E, but has only one letter?

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?

In an interview, a boy was asked an unusual question 'How two persons sitting with a table in between them can't see each other?' He was unable to reply. Can you?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

Can you find the missing piece of the Porsche?

What demands an answer, but asks no questions

I am the beginning of the end, and the end of time and space. I am essential to creation, and I surround every place. What am I?

How many times can you subtract the number 5 from 25?

What is more useful when it is broken?

What you cannot hold but it is yours?