Which is the smallest number that you can write using all the vowels exactly once?

A girl has as many brothers as sisters, but each brother has only half as many brothers as sisters. How many brothers and sisters are there in the family?

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?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?

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

SEVEN + SEVEN + SIX = TWENTY.

What are the digits ?

How do you go from 98 to 720 using just one letter?

Why is the Hole below a Lock?

What is full of holes but still holds water?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?