Five puzzles that broke the internet in 2015

Not every question has one right answer and the internet knows it best. Nothing really divided the world the way some puzzles did in 2015.

From math questions to the guessing the colour of the dress, here are the top five puzzles that baffled users across the world on various social media networks.

By the way, do we have a consensus on whether 5+5+5 is 15?

1) Dressgate

If you are an avid social media user, you wouldn't be a stranger to the dressgate. Alana MacInnes and Caitlin McNeill from Scotland posted a picture on Tumblr asking users whether the colour of the dress was gold and white or blue. The debate which started among family members and friends to decide the colour of the dress soon became an internet sensation.

The hashtag #TheDress took over Twitter with celebrities like Taylor Swift, Jaden Smith, Kim Kardashian, Ellen DeGeneres and more joining the debate. Professors and experts too jumped into the discussion explaining why some of us saw white and gold and others black and blue. Optical illusions and how the brain processes colours were some of the explanations put forth by experts.

What team were you on: #TheDressIsWhiteAndGold or #TheDressBlueAndBlack?

2) Is the cat going up or down?

The internet is obsessed with cats and anything that has to do with these feline beauties gets all the social love. So was the case with this 9Gag post of a cat walking on a set of stairs. The picture shows a cat with its paw and tail up on stairs.

Depending on what you think is right, the cat could be going up or. We all thought cats united the internet but this one actually divided it. If you are still interested in which direction the cat is moving, Business Insider explains it here.

3) When is Cheryl's birthday?

A maths problem which appeared in a test for Singapore's high school students worked up the internet. The question, in which a girl asks two boys to guess her age after giving them some clues, appeared in the test by Singapore and Asian School Math Olympiad (SOSMA). Test takers were asked to deduce Cheryl's age based on the clues given in the question.

Users on Facebook and Reddit gave detailed answers to this puzzle and whipped up the internet in a frenzy. In a Facebook post, SOSMA posted the full question and the model answer ending all speculations.

4) Mystery of the creepy, viral video

The video was sent to a Sweden-based technology news website called www.gadgetzz.com in the form of a CD form. It is a shaky video shot in an abandoned building with a guy wearing a cloak and a death mask gesturing to various visual codes. The background score is a noisy with a grating soundtrack. It makes for a perfectly coded creepy video.

Johny Krahbichler of GadgetZZ blogged about the video and posted it on Reddit to seeking answers. Apparently, the video was uploaded on YouTube in May but no one took any notice then. After Krahbichler's blog, interest in the video was revived. With the help of fellow Redditors and his blog's readers, Krahbichler has been able to decode some of the messages hidden in the video and they are indeed scary.

Whether it is a joke, a marketing stunt, a warning or something creepier, the verdict isn't out yet.

You can follow Krahbichler's Reddit thread here .

5) What is 5X3 by addition strategy?

Two questions in a mathematics exam in the US for third graders caught the internet in knots. In the first question, which was posted on Reddit, students were asked to "use repeated addition strategy to solve: 5x3". One student wrote "5x3=15" and substantiated the answer by writing "5+5+5" to show how he solved it but was marked negatively.

The second question asked them to "draw an array to show and solve: 4x6". The student drew six rows and four columns of dashes and wrote that the answer is 24. But he was again negatively marked.

The problems went viral on social media and there was considerable outrage about negative marking even though the answer was correct. Some of the arguments can be read here .

Hail the mysteries of the internet!