How can one talk without saying a single word?

Find the next number in the series

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

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

How many letters are in the alphabet?

You have three orange, two pink and five purple balls in the drawer beside your bed. There is no electricity and the room is entirely dark. How many balls must you take out to ensure at least one ball of each colour at least?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

A man is trapped in a room. The room has only two possible exits doors. Through the first door there is a room constructed from magnifying glass. The blazing hot sun instantly fries anything or anyone that enters. Through the second door there is a fire-breathing dragon. How does the man escape?

A man says, "Brothers and sisters, have I none, but that man's father is my father's son." Who is that man?

I speak without a mouth, and hear without ears. I have no-body, but I come alive with the wind. What am I?

Name the three-letter word that can complete the below words?

A) L O _ _ _ E
B) E D U _ _ _ E
C) _ _ _ E R
D) _ _ _ T L E