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Puzzles / Riddles

Puzzles and riddles are statements and questions framed such that they require ingenuity and imagination to resolve. Most are mathematical conundrums, but can also include the arcane, trivial or simply funny.

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I have an extension cord broken and I want to repair it.
It is closed with special head screws, which seems are made only to be tightened.
The head does not allow opening with a normal screwdriver.
I have a set of industrial, special screwdrivers, but none of them helps.
I tried to drill the head of the screw with gold type HSS drill bits, under 0.5 up to 2mm, but it is a very hard material and did not help.
The screws are fixed in plastic/aluminum case of the extension cord. They are not glued. They just need to be unscrewed.
So, how shall loose/open these screws?

Any helpful hint is appreciated.

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I'd like to come up with some clever tagline or rhyme for having our users reboot on Thursday.  After we push security updates to endpoints, I want the users to reboot, so I'd like a clever tagline.  For example, if I wanted my users to drink more water, I could say something like, "It's Thirsty Thursday, please make sure you drink plenty of water today!"  Or if I wanted my users to attend a meeting on Tuesday, "It's Technology Tuesday, please come to our technology meeting today!"

Can someone come up with a clever idea because "Reboot Thursday" or "Restart Thursday" just doesn't have a good ring to it!
What is the next number in the series : 1,2,4,8 ...
refresh tropical mango
squeezed zero lemonade
rise zero orange.
focus kiwi strawberry
Some catchy phrase needs to be in addition to those.
Dear Zons,


Could you please help me to become T1=T2k ?
Attached please find my pdf file for grace of God.

Thanking you in anticipation of  cyberspace solution and i remain,

With Faith, Love,  Trust & Pray:
B. Yoganand Patnaik
Puzzle 1

With this equation:

5+5+5 =550

With the addition of one line, make the equation correct. The one line is not through the equal sign making it a not equal sign.

Puzzle 2


In a similar manner to above, use 3 numbers to make the same total of 60. The three numbers have to be the same.

Puzzle 3

2 3 4 5 + =

Re-arrange the six characters such that it makes a balanced equation.
16 balls are given. All but one are of equal weight. You do not know whether the defective ball is lighter or heavier than the normal balls. You are given a comparison balance. You can use the balance only 3 times. How would you find out which is the defective ball? Is it heavier or lighter?
I am interested to know, in the year the gold standard was finally abandoned, 1971...

How many dollars were in circulation at the point in time?
It means that there are 88 things in the sky.
We have 12 players, and we would like to set up a 6 team round-robin tournament for a few different backyard games. We'd like to play as many different backyard games as possible with these 12 players (6 teams of 2 players), while ensuring that no two players get matched up more than once across the different games.

Looking for a grid of as many of these unique matchups (round robins) as mathematically possible.


Players: 1 - 12
Teams of 2
As many combination of 6 teams as mathematically possible while ensuring no two people end up together on a team more than once
Learn Ruby Fundamentals
LVL 12
Learn Ruby Fundamentals

This course will introduce you to Ruby, as well as teach you about classes, methods, variables, data structures, loops, enumerable methods, and finishing touches.

I have a school project and I have  to think of dollar words(words that equal a dollar) and I have to bring it in very soon so I am wondering if you have any tips or tricks to help me find dollar words fast
A restaurant is already taking bookings for Christmas parties.  There are 100 pre-orders for Pork Belly, 600 for Duck Breast, 152 for Halibut Fillet and 66 for Ox Liver. How many pre-orders are there for Caviar?
T & J adventure story characters
Here's an interesting coding puzzle:

A trader can perform two buys and two sells in a day of a given stock. An array of positive integers represents the share price of this stock at different times of the day (index i = 0 represents hour 1, i=1 represents hour 2, etc). The trader must always sell any current shares he has before he buys more shares. Write a function that determines the maximum profit the trader can make by buying and selling stock for a given day.

int maximizeProfit(int[] prices) {
   // Your code here

[10, 22, 5, 75, 65, 80]
The maximum profit is 87: buy at 10 sell at 22, buy at 5, sell at 80.

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The solution should have time complexity O(n).
Hello Fellow Experts!

I work with service dogs, and our family dog is a breeding dog for the program who is about to have her first litter.

I had the Idea of having her litters be named using a theme of Computers/Technology/Video games.

To do this we need to think of three (3) categories with Fifteen (15) names each that collectively fit this theme.

I need your help narrowing down categories, and coming up with more names for the categories we decide to use.

For example, I got the Idea for this by thinking it would be fun to name dogs these names:
  • Packet
  • Port
  • Socket

The program's organizer liked this Idea and said the would love to have a dog named TeraByte.

However, as I think of names they tend to come from all over and I can see multiple ways of categorizing them, and I tend to be picking names from all over as one big list making it hard to split up.

Here are some ways of Categorizing which I was considering:
  • Network/Internet Terms
  • Communication Software/Services
  • Productivity Software
  • Computer/Console Hardware
  • PC and Video Games
  • Technology professions and terms

Lets discuss which of these are good and whether there are others that might be better.

Here are additional names I have thought of, as you can see they could be categorized many ways:
  • MegaByte/MegaBit
  • FTP
  • email
  • twitter
  • hashtag
  • SQL (Pronounced Sequel) -- I figure we have to put the pronunciation down for anything not obvious to a non-technical person)
  • Java
  • Powershell
  • Sega
  • Atari
Here's an interesting brain teaser / programming puzzle I learned the other day. The answer can be achieved with a single line of code with computational complexity better then O(n).

N is a number that represents n boxes and n workers. All boxes are initially closed. Worker 1 goes through and toggles every box open. Worker 2 goes through and toggles every 2nd box (closed if open, open if closed). In the end, every worker i ⊂ N  has toggled every ith box opened or closed. Print the boxes that remain open at the end.

public void printOpenBoxes(n)
   // Implementation here

Open in new window


Expert Comment

by:Brian Matis
Fascinating! So, I'm curious, though... Did you figure this out via the underlying math of the situation, or by doing it the hard way and noticing the pattern in the results?

Author Comment

by:James Bilous
I saw the answer before I could figure it out. I just thought that it was a good lesson that you should always consider a simpler version to a problem before you waste a bunch of time diving too deep into a solution that is over complicated
Tori make ten-digit number using 0,1,2,3,4,5,6,7,8,9 by putting the digits in alphabetical order of their reversed names .what is tori's ten digit number.

I'm not hidden by a knife or spoon, figure this out and you might find me soon"
Black friday shopping!  Walmart and Staples has the 3600 on sale.  But there's a 3700.  higher number, I think is better?

But wikipedia says 3700 is only b/n/g (2.4GHz) and came out in October 2016.  the 3600 came out in april 2016 but has 2.4 / 5GHz.

trying to see the differences beyond that.  Can you help?

Amazon Web Services
LVL 12
Amazon Web Services

Are you thinking about creating an Amazon Web Services account for your business? Not sure where to start? In this course you’ll get an overview of the history of AWS and take a tour of their user interface.

1- Go to the place where knowledge sleeps
2-Follow the path that he left behind.
3-where data are tested and facts win out
4-Find what is labeled with a century less two.
5-Now name the phantom marked by cross and double lines.
What is the maximum distance of x in order to limit the slope change to less than .15 degrees?

It can be no hard for you guys, but my knowledge in cryptography or anything related is near to 0. So, if anyone can help me.

The puzzle is:

⬅ ➡ ↘


15, 41, 54, 59, 201, 255, 355

It's a 7 letters word.
Down here in NZ students have just recently sat a horrible algebra paper.  It appears that the examination authority didn't tell the teachers that changes were going to occur in the algebra exam so the teachers taught to what previous exams had asked for.  And all hell has broken loose.

So the attached graphic is a question that occurred in the exam.

I can do most of the paper (with a little bit of revision if I dig out the books) but the question above does not make sense to me.

So what do fellow experts make of it?  If anyone wants the full paper I can supply links.

I am working on below challenge

Psedo code:
1. create new array of given difference of size
2. loop through given array
3. fill the new array with given array starting from above difference till end
4. return new array as list
I wrote my code as below

public List wordsWithoutList(String[] words, int len) {
 int count=0;
 int origlen=words.length;
 int newLen=origlen-len;
 String[] arr=new String[newLen];
 for(int i=len-1;i<newLen;i++){
return Arrays.asList(arr);

Open in new window

I am not passing all tests
Expected      Run            
wordsWithoutList(["a", "bb", "b", "ccc"], 1) → ["bb", "ccc"]      ["a", "bb", "b"]      X      
wordsWithoutList(["a", "bb", "b", "ccc"], 3) → ["a", "bb", "b"]      [null]      X      
wordsWithoutList(["a", "bb", "b", "ccc"], 4) → ["a", "bb", "b", "ccc"]      []      X      
wordsWithoutList(["xx", "yyy", "x", "yy", "z"], 1) → ["xx", "yyy", "yy"]      ["xx", "yyy", "x", "yy"]      X      
wordsWithoutList(["xx", "yyy", "x", "yy", "z"], 2) → ["yyy", "x", "z"]      [null, "yyy", "x"]      X      

How to improve/modify my design, code and any other alternate approaches. please advise

I am working on below challenge

Psedo code:
1. create new array of given n size
2. loop through given array
3. fill the new array with given array
4. return new array
I wrote my code as below

public String[] wordsFront(String[] words, int n) {
 int count=0;
 String[] arr=new String[n];
for(int i=0;i<n;i++){
return arr;

Open in new window

I am passing all tests

How to improve/modify my design, code and any other alternate approaches. please advise

Puzzles / Riddles

Puzzles and riddles are statements and questions framed such that they require ingenuity and imagination to resolve. Most are mathematical conundrums, but can also include the arcane, trivial or simply funny.

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