What is black when you buy it, red when you use it, and gray when you throw it away?

Whats the next number in the below number sequence pattern.

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

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

An infinite number of mathematicians are standing behind a bar. The first asks the barman for half a pint of beer, the second for a quarter pint, the third an eighth, and so on. How many pints of beer will the barman need to fulfill all mathematicians' wishes?

What goes up but never comes down?

You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer and a five-minute timer, how can you boil the egg for only two minutes?

Find out the number of circles in the given picture having Illusion

What two things can you never eat for breakfast?

Begin with a word, five letters to my name,
Remove the first and last but I am the same
Take out my middle and still, I remain.
What word am I?