Our product and our sum always give the same answer. Who are we?

Count the Triangle in the figure given below:

How can you take 2 from 5 and leave 4?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

Move four matchsticks to the below square to form three squares?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

A man who was outside in the rain without an umbrella or hat didn’t get a single hair on his head wet. Why?

The answer I give is yes, but what I mean is no. What was the question?

Rebus Puzzle Definition: A rebus is an illusion device that uses pictures to represent words or parts of words.
What does This Rebus Puzzle Identify?

I have teeth but i don't bite. Who Am I ?