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.

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

A man had five children. He had $100 with him to give to his children. He decided to start with the youngest child and then give $2 more than each younger child to his next elder child.

For example, if he gives $x to the youngest child, he will give $(x+2) to the next one, $[(x+2) + 2] to the next one and so on.

Can you find out how much did the youngest one receive?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

A number can be multiplied by multiple of nine
i.e 9 18 27 36 45 ...

and the resulting number consist of only one digit.

Can you identify the number ?

Can you make the number 24 by utilizing the numbers 1, 3, 4 and 6? You must use one number only one time and you can use mathematical operation symbols anytime anywhere.

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

If in a car race, the man who came two places in front of the last man finished one ahead of the man who came fifth, how many contestants were there?