Which number should replace the question mark?

I go up and I go down.
I go up towards the beautiful sky and down toward the green ground.
I am present tense.
I am past tense too
Children love me.

Who Am I?

A girl is twice as old as her brother and half as old as her father. In 50 years, her brother will be half as old as his father. How old is the daughter now?

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

I have two coins.
* One of the coins is a faulty coin having a tail on both sides of it.
* The other coin is a perfect coin (heads on side and tail on other).

I blindfold myself and pick a coin and put the coin on the table. The face of the coin towards the sky is the tail.

What is the probability that another side is also tail?

A woman is sitting in her hotel room and hears a knock at the door. She opens the door to see a man whom she’s never met before. He says, “I’m sorry, I have made a mistake, I thought this was my room.” He then goes down the corridor and into the elevator. The woman goes back into her room and calls security. What made the woman so suspicious of the man?

Three friends named Mr. Black, Mr. Yellow and Mr. Green enter a pub on a weekend night. They are wearing either a Black, Yellow or Green shirt.

Mr. Yellow says to them, 'Did you notice that we all are wearing different color shirts than our names?'

To this, the man who was wearing the Green shirt said. 'Wow, thats right.'

Can you identify who is wearing which colour shirt ?

Can you solve the maths in the below-given picture equation?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

Alex opened 24 presents
Jonah opened 8 presents
Clara opened 1 present

Can you find out how many presents were opened by Candy?