Hard Riddles

Hard riddles with answers are a true test of your brain power, reasoning and comprehension. You are sure to find these tough difficult riddles both challenging and puzzling. While these hard riddles and answers may drive you a little crazy sometimes, they may surprise you in the way they force you think out of the box.

Diophantus Puzzle

Diophantus was a Greek mathematician. Little is known about the life of Diophantus except for an algebraic riddle from around the early sixth century. The riddle states:

Here lies Diophantus,’ the wonder behold.
Through art algebraic, the stone tells how old:
‘God gave him his boyhood one-sixth of his life,
One twelfth more as youth while whiskers grew rife;
And then yet one-seventh ere marriage begun;
In five years there came a bouncing new son.
Alas, the dear child of master and sage
After attaining half the measure of his father’s life chill fate took him.
After consoling his fate by the science of numbers for four years, he ended his life.’

How many years did Diophantus live based on the riddle?

Riddle Answer

Prisoners and Hats

Four prisoners named P1, P2, P3 and P4 are arrested for a crime, but the jail is full and the jailer has nowhere to put them. He eventually comes up with the solution of giving them a puzzle and if they answer correctly they can go free but if they fail they are to be executed.

The jailer makes prisoners P1, P2 and P3 stand in a single file. Prisoner P4 is put behind a screen. The arrangement looks like this:

P1 P2 P3 || P4

The ‘||’ is the screen.

The jailer tells them that there are two black hats and two white hats; that each prisoner is wearing one of the hats; and that each of the prisoners is only able to see the hats in front of them but not on themselves or behind. Prisoner P1 can see P2 and P3. Prisoner P2 can see P3 only. The fourth man, P4, behind the screen can’t see or be seen by any other prisoner. No communication between the prisoners is allowed.

If any prisoner can figure out and tell the jailer the color of the hat he has on his head all four prisoners go free. If any prisoner gives an incorrect answer, all four prisoners are executed. How the prisoners can escape, regardless of how the jailer distributes the hats?

You can assume that the prisoners can all hear each other if one of them tries to answer the question. Also, every prisoner thinks logically and knows that the other prisoners think logically as well.

Riddle Answer

Unreliable Clock

You have an unreliable clock. The clock loses exactly 24 minutes every hour. It is now showing 3:00am and you have set it correctly at midnight. The clock stopped 1 hour ago, what is the correct time now?

Riddle Answer

100 Blue Eyes

On a certain island there are people with assorted eye colors. There are 100 people with blue eyes and 100 people with brown eyes. Since there are no mirrors on this island, no person knows the color of their own eyes.

The people on the island are not allowed to talk or communicate with each other in any way. They are also not aware of the number of blue or brown eyed people on the island. For all they know, they could have red eyes too. But they are allowed to observe other people and keep count of the number of people with a certain eye color. There is a rule that the people on the island have to follow – any person who is sure of their eye color has to leave the island immediately.

One day, a person comes to the island and announces to the people that he sees someone with blue eyes. Everyone knows that the person only speaks the truth. What do you think happens?

Riddle Answer

Quarter Past Three

What’s the angle between the minute hand and hour hand at a quarter past three?

Riddle Answer

Hard Riddles

Diophantus Puzzle

Prisoners and Hats

Unreliable Clock

100 Blue Eyes

Quarter Past Three

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