Why Aeroplane windows are round?

A person was killed at a house party. When the police arrive, there are six people present in the house who are the friends of the victim. The name of the friends is Rohit, Aman, Nick, Gagan, and Randy.

Near the dead body, they find a few numbers written with blood by the victim on the floor. The numbers are 8, 5, 4, and 11.

The police arrests one of the friends for the murder. Whom did they arrest and why?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

What's the next in the series?

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

The more of this there is, the less you see. What is it?

What is red and smells like blue paint?

On rolling two dices (six-sided normal dice) together, what is the probability that the first one comes up with a 2 and the second one comes up with a 5?

What you cannot hold but it is yours?

Below, you can see three complete equations and one incomplete. Based on the three complete ones, can you complete the incomplete one?

5 $ 4 $ 3 $ 9 = 4215
6 $ 9 $ 2 $ 6 = 3816
4 $ 7 $ 3 $ 3 = 1122
7 $ 2 $ 7 $ 4 = ____

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?