What four weights can be used to balance from 1 to 30 pounds?

I have a five and a three-gallon jar. Assuming there is an infinite supply of water, how can I measure one-gallon water?

John and Jill are madly in love with each other. To remind Jill of his pure love, John wants to send her a ring by post but in their country where burglary is quite prominent, any package that is not locked comes under the risk of being stolen for the contents.

John and Jill possess many padlocks but neither one of them has the other key.

Can you find a way John can send the ring to Jill safely?

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?

Can you tell a 3D object that has just two surfaces?

The teacher told the student that if he told a lie then he will be expelled from school and if he told the truth then he still is expelled from school.

What can a student say to prevent his being expelled from school?

There is a bag which have 21 blue balls and 23 red balls. You also have 22 red balls outside the bag. Randomly remove two balls from the bag. * If they are of different colors, put the blue one back in the bag. * If they are the same colour, take them out and put a red ball back in the bag. Repeat this until only one ball remains in the bag. What is the color of the sole ball left in the bag ?

I have Rs.50 and I spend it in the way as below.

Thirty friends were on a hiking trip when they decided to enjoy the bonfire. They assembled for it and agreed to play a game. For that, they divided themselves into five teams with seven members each, forming five rows.

How did they manage to achieve this formation?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?