What is the fastest way to double your money?

Spot the cat in the picture below

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

Why do we preferably have round manhole covers and not square ones?

It has five wheels, though often think four, You cannot use it without that one more, You can put things in it, you can strap things on top, You can't find it in the market, but you can still go shop. What is it?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

John was driving a bus and got stuck when passing through an underpass. Then came Jacob with a needle and got the bus out of the underpass.

What did the boy do?

A Shopkeeper collects 71 rupees in the form of 20 paisa and 25 paisa.
He collects a total of 324 coins.

Can you tell me how many number of 20-paisa and 25-paisa he got?

What can you hold in your right hand, but never in your left hand?

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?