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.

No one wants to have it, but if one got it, he does not want to lose it. What is It?

In a classic wine shop, the list of three most popular wines are:
- The cost of 1 French wine bottle: 500$
- The cost of 1 German wine bottle: 100$
- The cost of 20 Dutch wine bottles: 100$

John entered the wine shop and he needs to buy
- All three types of wine bottles.
- Needs to buy Dutch wine bottles in multiples of 20.
- Need to buy 100 wine bottles in total.

John has only 10000$. How many wine bottles of each type, John must buy?

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

Solve the mathematical equation in the picture below.

2, 3, 5, 9, 17, _ What is the next number in the sequence?

Rearrange the letters in "new door" to make one word.