Best long riddles

In a supermarket, the first 25 customers of the day purchased an average of two items each. After a further 15 customers, the average number of items purchased by each customer rose to eight. What was the average number of items purchased by the last 15 customers only?

I look flat, but I am deep, Hidden realms I shelter. Lives I take, but food I offer. At times I am beautiful. I can be calm, angry and turbulent. I have no heart, but offer pleasure as well as death. No man can own me, yet I encompass what all men must have.

A group of campers have been on vacation so long, that they've forgotten the day of the week. The following conversation ensues. Darryl: "What's the day? I dont think it is Thursday, Friday or Saturday." Tracy: "Well that doesn't narrow it down much. Yesterday was Sunday." Melissa: "Yesterday wasn't Sunday, tomorrow is Sunday." Ben: "The day after tomorrow is Saturday." Adrienne: "The day before yesterday was Thursday." Susie: "Tomorrow is Saturday." David: "I know that the day after tomorrow is not Friday." If only one person's statement is true, what day of the week is it?

A man lives on the 44th floor of his building. On rainy days, when he gets home from work, he takes the elevator all the way up to his floor. But on sunny days, he goes up to floor 20 and walks the rest of the way. Why does he do this?

A man is found hanging in a room 30 feet off the ground. There is nothing else in the room except for a large puddle of water on the ground. The police can't see any way the man could have climbed the walls to get to where he is hanging. How did this man hang himself?

While I am in air, I am not in oxygen. I am also in water, but not in hydrogen. I am necessary in all animals, but you won't find me in the zoo. Look in all brains and you'll find me there too. What am I?

Five friends have their gardens next to one another, where they grow three kinds of crops: fruits (apple, pear, nut, cherry), vegetables (carrot, parsley, gourd, onion) and flowers (aster, rose, tulip, lily). They grow 12 different varieties. Everybody grows exactly 4 different varieties Each variety is at least in one garden. Only one variety is in 4 gardens. Only in one garden are all 3 kinds of crops. Only in one garden are all 4 varieties of one kind of crops. Pears are only in the two border gardens. Paul's garden is in the middle with no lily. Aster grower doesn't grow vegetables. Rose grower doesn't grow parsley. Nuts grower has also gourd and parsley. In the first garden are apples and cherries. Only in two gardens are cherries. Sam has onions and cherries. Luke grows exactly two kinds of fruit. Tulips are only in two gardens. Apples are in a single garden. Only in one garden next to the Zick's is parsley. Sam's garden is not on the border. Hank grows neither vegetables nor asters. Paul has exactly three kinds of vegetable. Who has which garden and what is grown where?

Two girls ate dinner together. They both ordered iced tea. One girl drank them very fast and had finished five in the time it took the other to drink just one. The girl who drank one died while the other survived. All of the drinks were poisoned. How is that possible?

A wealthy man lives alone in a small cottage. Being partially handicapped, he had everything delivered to his cottage. The mailman was delivering a letter one Thursday when he noticed that the front door was ajar. Through the opening he could see the man's body lying in a pool of dried blood. When a police officer arrived he surveyed the scene. On the porch were two bottles of warm milk, Monday's newspaper, a catalog, flyers, and unopened mail. The police officer suspects it was foul play. Who does he suspect and why?

You are on your way to visit your Grandma, who lives at the end of the valley. It's her anniversary, and you want to give her the cakes you've made. Between your house and her house, you have to cross 5 bridges, and as it goes in the land of make believe, there is a troll under every bridge! Each troll, quite rightly, insists that you pay a troll toll. Before you can cross their bridge, you have to give them half of the cakes you are carrying, but as they are kind trolls, they each give you back a single cake. How many cakes do you have to leave home with to make sure that you arrive at Grandma's with exactly 2 cakes?