Good Riddles

Question: No matter how hard you try,
I can open what you can't.
If it wasn't for me,
on your front porch you would stand.

What am I?

Question: A smart landscaper is given the task of placing 4 trees so that they are all the same distant away from each other.

How does he do this?

Question: I was taking a plane to China and almost missed my flight. On my way to the terminal there were 7 other girls walking in the opposite direction. Each of these girls had 8 purses and each purse had 2 dogs.

How many in all were on the plane?

Question: Fill in the blank: Ebere is the Michael's daughter. So Michael is the ____ of Ebere's father?

Question: What comes down and never goes up?