Best Riddles of September 2010

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.

What 5-digit number has the following property? If we put numeral 1 in front of the number, we get a number three times smaller, than if we put the numeral 1 behind this number.

man gave one son 10 cents and another son was given 15 cents. What time is it?

What is the four digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

There are three Athletes (Lavesh, Tarun and Harish) and their individual Coaches (Meher, Meenaxi and priyanka) standing on the shore.
No Coach trusts their Athlete to be near any other Coach unless they are also with them.
There is a boat that can hold a maximum of two persons.
How can the six people get across the river?

Three Brothers are identical triplets. The oldest by minutes is Lavesh, and Lavesh always tells anyone the truth. The next oldest is Tarun, and Tarun always will tell anyone a lie. Harish is the youngest of the three. He sometimes lies and sometimes tells the truth.
Ganpat, an old friend of the family's, came over one day and as usual he didn't know who was who, so he asked each of them one question.
Ganpat asked the brother that was sitting on the left, "Which brother is in the middle of you three?" and the answer he received was, "Oh, that's Lavesh."
Ganpat then asked the brother in the middle, "What is your name?" The response given was, "I'm Harish."
Ganpat turned to the brother on the right, then asked, "Who is that in the middle?" The brother then replied, "He is Tarun."
This confused Ganpat he had asked the same question three times and received three different answers.
Who was who?

What mathematical symbol can be placed between 5 and 9, to get a number greater than 5 and smaller than 9?

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different.

How do you measure 45 minutes?

You are mixing cement and the recipe calls for five gallons of water. You have a garden hose giving you all the water you need. The problem is that you only have a four gallon bucket and a seven gallon bucket and nether has graduation marks. Find a method to measure five gallons.