Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not-rounded numerals equals 24.

Spelt forwards I’m what you do every day, spelled backwards I’m something you hate. What am I?

We know that the number 7 is the prime followed by a cube. Which next number is also a prime followed by a cube?

The day after tomorrow will be three days before Tuesday. Can you find out what is today?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

There are three light switches outside a room. One of the switches is connected to a light bulb inside the room.
Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb?

A quarter is one-fourth of a dollar but Mr. John has changed the equation as below :

DOLLAR * 4 = QUARTER

Can you replace each letter with a digit to make the above solution correct?

What begins with T, ends with T, and has T in it?

Can you count the number of quadrilaterals in the picture below?