What is the Surname of Barbie Doll?

What does a man do only once in his lifetime, but women do once a year after they are 29?

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?

Every words stands for unique digit that makes the arithmetic equation true

SEVEN + SEVEN + SIX = TWENTY.

What are the digits ?

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

John has played 50 ODI's and his average is 50. How many runs should he score in his 51st ODI, so that his average score jumps to 51?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

What has a bottom at the top?

I possess a head

I flaunt a tail

But I don't have mouth or legs

Can you find out who I am?

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??