When my father was 31 I was 8. Now he is twice as old as me. How old am I?

Here is a mathematical expression that also secretly tells a movie name. What movie is that?

There are two beautiful yet remote islands in the South Pacific. The Islanders born on one island always tell the truth, and the Islanders from the other island always lie.
You are on one of the islands and meet three Islanders. You ask the first which island they are from in the most appropriate Polynesian tongue, and he indicates that the other two Islanders are from the same island. You ask the second Islander the same question, and he also indicates that the other two Islanders are from the same island.
Can you guess what the third Islander will answer to the same question?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

If an electric train is travelling south, then which way is the smoke going?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

You have an empty wine bottle with a cork that has been secured at the top in a normal way. There is a metal ring inside the bottle that is suspended by a string.

How can you make the metal ring drop to the bottom if you are not allowed to touch anything - not the bottle, not the cork, not the thread and not the ring?

You have 10 balls with you. A friend of yours out of nowhere asks you to place those ten balls in five lines such that each of the lines has exactly 4 balls on them. He needs to check your intelligence. Prove him by doing the task.

No matter how little or how much you use me, you change me every month. What am I?

What does below chemistry rebus means?