What occurs twice in a week, once in a year but never in a day?

Begin with a word, five letters to my name,
Remove the first and last but I am the same
Take out my middle and still, I remain.
What word am I?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

My grandson is about as many days as my son in weeks, and my grandson is as many months as I am in years. My grandson, my son and I together are 120 years. Can you tell me my age in years ?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

Can you find a five letter word that is left with only two letters if one is removed?

My thunder comes before lightning.
My lightning comes before my rain.
My rain dries up all the land it touches.

Who am I?

What does below science rebus mean?

Ag Ag Ag
Ag SPOON Ag
Ag Ag Ag

What always comes into a house through the keyhole?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?