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

Can you find out the total number of triangles in the given figure?

Decode below rebus
D
N
A
T
S , D

A mad serial killer kidnaps people and forces them to play the game of 2 pills with them, In this game, there are pills in the table and one of them is normal pill while the other one is deadly poisonous.
The victim will choose one pill and the killer will pick the other pill and both simultaneously will swallow the pill with water.
victim dies every time.

One day the serial killer kidnaps the Joseph and forces him to play the same game with him.

Joseph solves the mystery of the two pills and remains alive.

Explain?

_ _ _ IE _ _
_ _ _ IE _
_ _ IE _ _
_ _ IE _
_ _ _ _ IE

Like you see, some letters have gone missing from these words that contain the IE pair at some or the other place. The letters that will be used to fill the blanks are given below. Use them and form meaningful words. Can you do that?

A, C, D, F, H, K, L, M, N, N, O, R, R, S, S, S, T, T, Y and Y.

Solve below rebus puzzle?

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

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Find the next number in the series

12, 20, 40, 72, 116, 172 ?