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?

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 has one letter and starts with an E?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

Can you solve this picture maths equation?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

He does not have any heart but still, He manages to live.
If you kill him, you will eventually die but yet you kill him.
He cannot run, who is He?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.