Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

If you drop a 15 kg iron bar and a 5 kg bag of cotton from a height of 50 meters which will reach the ground first?

Why is a river so rich ?

A man is lying dead in a field where no one is around. His head is split open and his legs are disfigured. Near to him, there is an unopened package. No living organism can be found anywhere at the crime scene.

How did he die?

You need to cut a round cake into eight equal pieces with just 3 cuts. Can you do it?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

Can you count the number of children in the picture below

What Deficiency does the below rebus represent?

VIT_MIN

A Car driver was heading down a street in Washington. He went right past a stop sign without stopping, he turned left where there was a 'no left turn' sign and he went the wrong way on a one-way street. Then he went on the right side of the road past a cop car. Still, he didn't break any traffic laws. Why not?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.