Worlds Hardest Riddles With Answers 1 : River Riddle
Difficulty ★★★★☆
Popularity ★★★★★
Four people need to cross a dark river at night.They have only one torch and the river is too risky to cross without the torch. if all people cross simultaneous then torch light wont be sufficient.Speed of each person of crossing the river is different.cross time for each person is 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the river ?
Answer & Explanation
Solution:
The initial solution most people will think of is to use the fastest person as an usher to guide everyone across. How long would that take? 10 + 1 + 7 + 1 + 2 = 21 mins. Is that it? No. That would make this question too simple even as a warm up question.
Let's brainstorm a little further. To reduce the amount of time, we should find a way for 10 and 7 to go together. If they cross together, then we need one of them to come back to get the others. That would not be ideal. How do we get around that? Maybe we can have 1 waiting on the other side to bring the torch back. Ahaa, we are getting closer. The fastest way to get 1 across and be back is to use 2 to usher 1 across. So let's put all this together.
1 and 2 go cross
2 comes back
7 and 10 go across
1 comes back
1 and 2 go across (done)
Total time = 2 + 2 + 10 + 1 + 2 = 17 mins
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Worlds Hardest Riddles With Answers 2 : Popular Age Problem
Difficulty ★★★★☆
Popularity ★★★★★
Two old friends, Jack and Bill, meet after a long time.
Three kids
Jack: Hey, how are you man?
Bill: Not bad, got married and I have three kids now.
Jack: That"s awesome. How old are they?
Bill: The product of their ages is 72 and the sum of their ages is the same as your birth date.
Jack: Cool..But I still don"t know.
Bill: My eldest kid just started taking piano lessons.
Jack: Oh now I get it.
How old are Bill"s kids?
Answer & Explanation
Solution:
3,3,8
Lets break it down. The product of their ages is 72. So what are the possible choices?
2, 2, 18 sum(2, 2, 18) = 22
2, 4, 9 sum(2, 4, 9) = 15
2, 6, 6 sum(2, 6, 6) = 14
2, 3, 12 sum(2, 3, 12) = 17
3, 4, 6 sum(3, 4, 6) = 13
3, 3, 8 sum(3, 3, 8 ) = 14
1, 8, 9 sum(1,8,9) = 18
1, 3, 24 sum(1, 3, 24) = 28
1, 4, 18 sum(1, 4, 18) = 23
1, 2, 36 sum(1, 2, 36) = 39
1, 6, 12 sum(1, 6, 12) = 19
The sum of their ages is the same as your birth date. That could be anything from 1 to 31 but the fact that Jack was unable to find out the ages, it means there are two or more combinations with the same sum. From the choices above, only two of them are possible now.
2, 6, 6 sum(2, 6, 6) = 14
3, 3, 8 sum(3, 3, 8 ) = 14
Since the eldest kid is taking piano lessons, we can eliminate combination 1 since there are two eldest ones. The answer is 3, 3 and 8.
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Worlds Hardest Riddles With Answers 3 : Who Is The Killer Puzzle
Difficulty ★★★★☆
Popularity ★★★★☆
Tarun Asthaniya is found dead in his office at his desk. The police have narrowed the suspects down to three people: Mrs. Harish Kumar, Taruns's wife Himanshi Asthaniya and his business partner Mr. Jason Negi . All three visited Tarun on the day of his murder, but all three provide the police with stories of explanation as to the reason for their visit.
Police found Mr. tarun with his wrist watch still on his right arm, a torn up picture of his wife laying on the floor beside the trash can, and an ink pen in his right hand. On the desk, the police found a name plate, a telephone that was off the hook, and a personal calendar turned to the July 5th page with 7B91011 written on it. After examining this evidence, the police knew their suspect. Who was it ?
Answer & Explanation
Solution:
Jason Negi
the number on the calendar was written in a hurry , police matched the written number with the months of the year. So the B was an 8, thereby giving us 7-8-9-10-11: July, August, September, October, November. Use the first letter of each month and it spells J-A-S-O-N.
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Worlds Hardest Riddles With Answers 4 : Brain Twister Puzzle
Difficulty ★★★★☆
Popularity ★★★★★
2+3=8,
3+7=27,
4+5=32,
5+8=60,
6+7=72,
7+8=??
Solve it?
Answer & Explanation
Solution:
98
2+3=2*[3+(2-1)]=8
3+7=3*[7+(3-1)]=27
4+5=4*[5+(4-1)]=32
5+8=5*[8+(5-1)]=60
6+7=6*[7+(6-1)]=72
therefore
7+8=7*[8+(7-1)]=98
x+y=x[y+(x-1)]=x^2+xy-x
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Worlds Hardest Riddles With Answers 5 : Hardest Balance Logic Puzzle
Difficulty ★★★★★
Popularity ★★★★★
You are given a set of scales and 12 marbles. The scales are of the old balance variety. That is, a small dish hangs from each end of a rod that is balanced in the middle. The device enables you to conclude either that the contents of the dishes weigh the same or that the dish that falls lower has heavier contents than the other.
The 12 marbles appear to be identical. In fact, 11 of them are identical, and one is of a different weight. Your task is to identify the unusual marble and discard it. You are allowed to use the scales three times if you wish, but no more.
Note that the unusual marble may be heavier or lighter than the others. You are asked to both identify it and determine whether it is heavy or light.
Answer & Explanation
Solution:
So that the following plan can be followed, let us number the coins from 1 to 12. For the first weighing let us put on the left pan coins 1,2,3,4 and on the right pan coins 5,6,7,8.
There are two possibilities. Either they balance, or they don't. If they balance, then the different coin is in the group 9,10,11,12. So for our second one possibility is to weigh 9,10,11 against 1,2,3
(1) They balance, in which case you know 12 is the different coin, and you just weigh it against any other to determine whether it is heavy or light.
(2) 9,10,11 is heavy. In this case, you know that the different coin is 9, 10, or 11, and that that coin is heavy. Simply weigh 9 against 10; if they balance, 11 is the heavy coin. If not, the heavier one is the heavy coin.
(3) 9,10,11 is light. Proceed as in the step above, but the coin you're looking for is the light one.
That was the easy part.
What if the first weighing 1,2,3,4 vs 5,6,7,8 does not balance? Then any one of these coins could be the different coin. Now, in order to proceed, we must keep track of which side is heavy for each of the following weighings.
Suppose that 5,6,7,8 is the heavy side. We now weigh 1,5,6 against 2,7,8. If they balance, then the different coin is either 3 or 4. Weigh 4 against 9, a known good coin. If they balance then the different coin is 3, otherwise it is 4. The direction of the tilts can tell us whwther the offending coin is heavier or lighter.
Now, if 1,5,6 vs 2,7,8 does not balance, and 2,7,8 is the heavy side, then either 7 or 8 is a different, heavy coin, or 1 is a different, light coin.
For the third weighing, weigh 7 against 8. Whichever side is heavy is the different coin. If they balance, then 1 is the different coin. Should the weighing of 1,5, 6 vs 2,7,8 show 1,5,6 to be the heavy side, then either 5 or 6 is a different heavy coin or 2 is a light different coin. Weigh 5 against 6. The heavier one is the different coin. If they balance, then 2 is a different light coin.
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Worlds Hardest Riddles With Answers 6 : Unlock The Distance Puzzle
Difficulty ★★★★★
Popularity ★★★★★
Distances from you to certain cities are written below.
BERLIN 200 miles
PARIS 300 miles
ROME 400 miles
AMSTERDAM 300 miles
CARDIFF ??? miles
How far should it be to Cardiff ?
Answer & Explanation
Solution:
100 miles. Each vowel is worth 300 and each consonant is worth -100. These are totalled in each city name to give the distance
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Worlds Hardest Riddles With Answers 7 : Logic Interview Question
Difficulty ★★★★☆
Popularity ★★★★★
The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.
Boxes are labeled but all labels are wrong!
You are allowed to open one box, pick one ball at random, see its color and put it back into the box, without seeing the color of the other ball.
How many such operations are necessary to correctly label the boxes?
Answer & Explanation
Solution:
Just One!
Because we know all labels are wrong.
So the BW box must be either BB or WW. Selecting one ball from BW will let you know which.
And the other two boxes can then be worked out logically.
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Worlds Hardest Riddles With Answers 8 : Hard Measuring Water Riddle
Difficulty ★★★★★
Popularity ★★★★★
You have two buckets of 11liter and 6liter.
How can you measure exactly 8liter ?
Answer & Explanation
Solution:
Steps 11-Liter 6Liter
1. 11 -
2. 5 6
3. 5 0
4. 0 5
5. 11 5
6. 10 6
7. 10 0
8. 4 6
9. 4 0
10. 0 4
11. 11 4
12. 9 6
13. 9 0
14. 3 6
15. 3 0
16. 0 3
17. 11 3
18. 8 6 ==> got it
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Worlds Hardest Riddles With Answers 9 : Logic Escape Problem
Difficulty ★★★★☆
Popularity ★★★★★
In the kingdom of skull, King Norse did not allow any citizen to visit the world outside. Also only a person with a proper paperwork was allowed to enter or he was sent back. A wooden bridge was what connected the kingdom to the world. The king had appointed a sharpshooter who would check every five minutes on the bridge to check. After checking, he would go back to his hut and return exactly after five minutes again. The bridge took 9 minutes to cross.
A merchant was able to escape the kingdom without harming the shooter.
How ?
Answer & Explanation
Solution:
The merchant walked across the bridge for almost five minutes when the shooter was inside the bridge. Then he turned and started walking back to the kingdom of skull. On approaching the kingdom, he was asked of papers which he never had. Thus he was sent back.
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Worlds Hardest Riddles With Answers 10 : Sherlock Holmes Cipher Puzzle
Difficulty ★★★★★
Popularity ★★★★☆
Sherlock, A detective who was mere days from cracking an international smuggling ring has suddenly gone missing. While inspecting his last-known location, you find a note:
710 57735 34 5508 51 7718
Currently there are 3 suspects: Bill, John, and Todd. Can you break the detective's code and find the criminal's name?
Answer & Explanation
Solution:
Bill. If you read the message upside down, you'll notice that the numbers resemble letters and that those letters form legible sentences. The message is 'Bill is boss. He sells oil.'
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