A word I know has six letters it contains, remove one letter and 12 remain. What is it?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

Find the value of "?" in the ball picture Riddle below:

John and Jenni are a married couple. They have two kids, one of them is a girl. Assume safely that the probability of each gender is 1/2.
What is the probability that the other kid is also a girl?

Hint: It is not 1/2 as you would first think.

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

"That Restaurant always remains crowded. This is the reason why nobody goes there".

Can you find a flaw in this statement?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

How many triangles can you count in the figure given?

What month of the year has 28 days?