It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

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 count the number of seconds in a year?

Clue: You need to bother about calculation.

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

In a football game, Christina defeated Teresa by 2 - 0 but no man from either side scored. How can this be possible?

John drives to his office at 20km/hr. After reaching the office, he realizes that today is a holiday. He went back at an average speed of 30km/hr. Discounting the time spent in the stoppage what was the average speed of his journey?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?