There are 6561 balls. Out of them 1 is heavy. Find the minimum number of times the balls have to be weighed for finding out the heavy ball.

When purchased together, a pair of binoculars and the case cost $100. If the binoculars cost $90 more than the case, how much does the case cost?

The number of bacteria in a large sealed jar doubles every minute. The bacteria will take an hour to fill the jar. When will the jar be half full?

If the price off a dress was cut by 20% for a sale, by what percentage off the sale price must it be increased by to resell it at the original price?

If I had one more sister I would have twice as many sisters as brothers. If I had one more brother I would have the same number of each. How many brothers and sisters have I?

What letter is two to the right of the letter which is four to the left of the letter which is immediately to the right of the letter four to the right of the letter C below? A B C D E F G H

At six o’clock the wall clock struck 6 times. Checking with my watch, I noticed that the time between the first and last strokes was 30 seconds. How long will the clock take to strike 12 at midnight?

There are 25 red balls, 47 green balls and 3 blue balls in a basket. There is a blind man. What is the minimum number of balls that the blind man has to pick to make sure that there are at least 2 balls of different colors?

You need to boil eggs for exactly 9 minutes. But you have only 2 hourglasses – one measures 4 minutes and the other measures 7 minutes. How do you measure exactly 9 minutes without the process taking longer than 9 minutes?.

A man has 53 socks in his drawer: 21 identical blue, 15 identical black and 17 identical red. The lights are fused and he is completely in the dark. How many socks must he take out to be 100 percent certain he has a pair of black socks?

A man goes to a hardware shop and asks for the price of an item. The shop keeper replies that the item is “one for $1″. The man gives the shop keeper “$3 for 600″. What did the man buy for his newly painted house?

A contractor is doing work for 7 days at your home. You have a gold bar that is worth $7000. You need to pay him $1000 every day and $7000 in total. You have to pay him in gold by using the gold bar. How can you pay him $1000 worth of gold everyday by cutting the gold bar only twice?

A bathtub has two taps and a plug hole. The cold tap on its own fills the bathtub in 18 minutes. The hot one on its own fills the bathtub in 15 minutes. The plug hole can drain the bathtub in 10 minutes with the taps off. How long will the bathtub take to fill if both taps are turned on and the plug left out?

You need to check that your friend, Bob, has your correct phone number, but you cannot ask him directly. You must write the question on a card and give it to Eve who will take the card to Bob and return the answer to you. What must you write on the card, to ensure Bob can encode the message so that Eve cannot read your phone number?

There are 21 barrels of wine with a farmer. 7 are full, 7 are half full and 7 are empty. He wishes to divide them among his three sons such that each son has the same number of full barrels, the same number of half full barrels, and the same number of empty barrels. Note that there are no measuring devices handy. How can the barrels and wine be evenly divided?