Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

Whats the next number in the below number sequence pattern.

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

What has one eye, but can’t see?

Can you count the number of triangles in the given picture?

There are 20 people in an empty, square room. Each person has full sight of the entire room and everyone in it without turning his head or body, or moving in any way (other than the eyes). Where can you place an apple so that all but one person can see it?

You measure my life in hours
I serve you by expiring
I vanish faster when I am thin
and slower when I am thick
The wind is my energy
What am I?

Can you name an animal whose killing cannot be performed without spilling your own blood?

Can you write down eight eights so that they add up to one thousand?

Two fathers and two sons decided to go to a shop and buy some sweets upon reaching. Each of them bought 1 kg of sweet. All of them returned home after some time and found out that they had 3kg of sweets with them.

They did not eat the sweets in the way, nor threw or lose anything. Then, how can this be possible?