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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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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.
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Concerto's Cloud Advisory Services

Want to avoid the missteps to gaining all the benefits of the cloud? Learn more about the different assessment options from our Cloud Advisory team.

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
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
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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

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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?

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
Lessons on Wi-Fi & Recommendations on KRACK
Lessons on Wi-Fi & Recommendations on KRACK

Simplicity and security can be a difficult  balance for any business to tackle. Join us on December 6th for a look at your company's biggest security gap. We will also address the most recent attack, "KRACK" and provide recommendations on how to secure your Wi-Fi network today!


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
I've got an ongoing issue with my wi-fi networks. When downloading files from the internet, or moving files around the network, the network traffic as shown in task manager repeatedly drops to zero every 7 seconds, like clockwork. I've attached a screenshot of the task manager on my laptop showing the bandwidth doing this. This happens all the time, 100%.

The thing is - this happens on both my laptop wi-fi, and on my desktop wi-fi, and persists on my desktop whether I use a D-Link PCI-E adaptor or a TP-Link USB adaptor. It's exactly the same symptom on all my devices. All devices are connecting using wireless N protocol, all computers are running Windows 10.

So I was thinking this would point to a router issue - I was using an Asus RT-N16, so after various troubleshooting methods on that I replaced the firmware with DD-WRT thinking that might finally sort it, and it did not. So I guessed it might be a hardware issue with the router, so I've just bought a new router - a D-Link DIR 842 - and now with the old router disconnected and the brand new one in place, it's still doing it. I'm still seeing exactly the same drop-outs, on 3 completely different pieces of hardware.

I don't think it's an interference issue particularly as we live right on the edge of the city (there's fields behind my house) with minimal wi-fi traffic from neighbours, and it's an old stone house with really thick walls that you can't even pick up a mobile phone signal through. Also I first noticed …
Using the LT Chunker developed at the University of Edinburg I have developed code
that highlights noun verbs and phrases,

I have an advanced degree in computer science,  my project was scraped ten years ago
and I am now trying to restart

You will have to sign a non-compete

Expert knowledge in K&R ATT 'C' programming,   MySQL ( looking to migrate to Oracle) ,  PHP

Need help installing library

I can send you a copy of the EXE and if you can install it successfully
on a Linux Server  and I can successfully install on my server I will pay well
I need your help to identify the song below:

It sounds so familiar from Youtube, but I cannot remember it.
It may be soundtrack or instrumnetal.
I am doing a research for the subject medicine.

Do you have the encounter with this medicine?

Tell me your experience.

Or, just help me to look up medical information.

I have two separate column of number sets.  I want to compare the two and come up with a 3rd column set of numbers from column A that don't have any of the sets of numbers in column B.


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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Puzzles / Riddles