Hard Riddle - How Many Planes?

The main resemblance of all the hardest hard riddles is that they all seem very difficult and unsolvable, but when you read the solution, you'll feel sorry and think that you should be able to find the answer at the first place.

This time hardest riddle, "How Many Planes?", is probably the same too. Just try to use your logic and little math to solve this one, and think thoroughly before giving up, as you'll find that this puzzle is actually can be solved quite easily.

So, here goes:

On a secret island, there is an lab and airport conducts a research of some new generation of airplanes. Now the airport is the home base of an unlimited number of identical airplanes. Each airplane has a fuel capacity to allow it to fly exactly 1/2 way around the world, along a great circle.

The planes have the ability to refuel in flight without loss of speed or spillage of fuel. Though the fuel is unlimited, the island is the only source of fuel.

Question: What is the fewest number of aircraft necessary to get one plane all the way around the world assuming that all of the aircraft must return safely to the airport? Explain your answer!

Notes:

• Each airplane must depart and return to the same airport, and that is the only airport they can land and refuel on ground.
• Each airplane must have enough fuel to return to airport.
• The time and fuel consumption of refueling can be ignored. (so we can also assume that one airplane can refuel more than one airplanes in air at the same time.)
• The amount of fuel airplanes carrying can be zero as long as the other airplane is refueling these airplanes.

Difficulty:

{[['']]}

The Missing Dollar

I don't know whether this riddle can be categorized as hard or tricky. Heck, I don't even know if it's even a riddle. The reason why I put this in the hardest hard riddles section is merely because this one managed to drive me crazy for some times. So, try this one and see if it will have the same effect on you:


Three friends check into a hotel for the night and the receptionist tells them that the bill is $30, payable in advance. So, they each pay him $10 and go to their room.

A few minutes later, the receptionist realizes he has made an error and overcharged the trio by $5. He asks the bellboy to return $5 to the 3 friends who had just checked in.


The bellboy sees this as an opportunity to make $2 as he reasons that the three friends would have a tough time dividing $5 evenly among them; so he decides to tell them that the clerk made a mistake of only $3, giving a dollar back to each of the friends. He pockets the leftover $2 and goes home for the day!

Now, each of the three friends gets a dollar back, thus they each paid $9 for the room which is a total of $27 for the night. We know the bellboy pocketed $2 and adding that to the $27, you get $29, not $30 which was originally spent.

Where did the other dollar go?

Difficulty:

{[['']]}

Moral Dilemma Riddle

I don't know if this one can be called as hard riddle or not, but it's obviously one of the best riddles in my opinion. It's a puzzle that once asked during a job interview, because it can show how someone manage when he has to face a moral dilemma situation. Better yet, this test also can show whether a person can thinking out of the box or not.

So, here goes:

You are driving alone in your two-seats sports car on a wild, stormy night. You pass by a bus stop and you see three people waiting for the bus:


A sick old lady who looks as if she is about to die.
An old friend who once saved your life, and almost late to once in a lifetime meeting.
The perfect man/woman you have been dreaming about.

Question: Which one would you choose to offer a ride to, knowing that there could only be one passenger in your car?

Hint: You could pick up the old lady, because she is going to die, and thus you should save her first; or you could take the old friend because he once saved your life, and this would be the perfect chance to pay him back. However, if you take one of those persons and come back, there's no way that your perfect dream lover is still there.

Difficulty:

{[['']]}

Detective Puzzle: Who's The Killer and Victim?

Well, this one is not really a detective puzzle or riddle, because the victim is still unknown too. Actually, this is probably just a simpler version of Einstein's Riddle that I posted before. Although not as difficult, this one still can be considered as one of the hardest hard riddles. Can you solve it?


There are five people. One of them shot and killed one of the other five. Which man is the murderer?

1. Dan ran in the NY City marathon yesterday with one of the innocent men.
2. Mike considered being a farmer before he moved to the city.
3. Jeff is a topnotch computer consultant and wants to install Ben's new computer next week.
4. The murderer had his leg amputated last month.
5. Ben met Jack for the first time six months ago.
6. Jack has been in seclusion since the crime.
7. Dan used to drink heavily.
8. Ben and Jeff built their last computers together.
9. The murderer is Jack's brother. They grew up together in Seattle.

Do you know who's the killer and who's the victim?

Difficulty:

{[['']]}

Albert Einstein's Riddle

Albert Einstein's riddle, also known as zebra puzzle, is a well-known logic puzzle. It is said that Einstein invented this puzzle when he was a boy, although there's no evidence or confirmation about his authorship. This riddle was first published by Life International magazine on December 17, 1962.

It is sometimes claimed that 98% of the world's population can't solved it. Check the Einstein's riddle below, and see if you're included in the elite 2% of intelligent people.

1. There are five houses.
2. The Englishman lives in the red house.
3. The Spaniard owns the dog.
4. Coffee is drunk in the green house.
5. The Ukrainian drinks tea.
6. The green house is immediately to the right of the ivory house.
7. The Old Gold smoker owns snails.
8. Kools are smoked in the yellow house.
9. Milk is drunk in the middle house.
10. The Norwegian lives in the first house.
11. The man who smokes Chesterfields lives in the house next to the man with the fox.
12. Kools are smoked in a house next to the house where the horse is kept.
    
13. The Lucky Strike smoker drinks orange juice.
14. The Japanese smokes Parliaments.
15. The Norwegian lives next to the blue house.

Rules:

• Each of the five houses is painted a different color.
• Their inhabitants are of different national extractions, own different pets, drink different beverages and smoke different brands of American cigarets.
• In statement 6, right means your right.

Question: Who drinks water? Who owns the zebra?

Difficulty:

{[['']]}