#math riddle

[joe-bou-khalil-projects]

Fun math problem to try and solve. Read the problem and try to solve it. And if you want to see the solution. Try and solve it.

[wtf-tfw]

Josh is heading west to see his friend Niall for the winter (nonsexual). If Niall lives 433 milks away from Josh's house, and Josh wants to get to Niall's house as quickly as possible (for nonsexual reasons) and wants the most economic option, which train should he take?

Train A: travels at a speed of 300 mph and makes 2 stops that take 40 minutes each to let bunny rabbits cross. The ticket costs $95 for adults but incurs a $2 discount if you have both of your big toes intact.

Train B: travels at a speed of 55 mph and makes no stops but serves fish which makes Josh sick, and the ticket is $54 dollars for adults.

[zin3724]

Sudoku Cayley Table

Take a completed sudoku, and append an identity row to the top, and identity column to the left.

You now have the Cayley table of a magma with identity. Is the magma also monoid? a group?

What if you relax the subgrid condition? (idk if there's an official name for it, but you know...)

Is that true for \(n\times n\) grids for all \(n\in\mathbb{N}\)?

Is that true for an infinite grid? (countable, surely, otherwise you can't even have a row containing all the elements!)

[test4exams-blog]

Best 15 Math Riddles That Even Your Teacher Will Fail | Test 4 Exams

Best 15 math riddles that will exercise your brain. Physical exercise is important but mental exercise is more important for brain health.

[hereeverything]

Find out the missing number?

[danskjavlarna]

Source details and larger version.

Gazing out over the sands of Egypt for thousands of years: strange sphinxes share their riddles in my sphinx gallery.

[hemoglobox]

Pi-riddle answer

My sickness from yesterday continued, so I am posting this on 3/16. :( but here is the answer to the Pi-riddle from “yesterday”.

Recap. Q: "You are stranded in a small, unmanned island. All you got is a stick and a coconut. You got a head-concussion, so you forgot a lot of things, like, for the love of god, you forgot what Pi is. You suddenly experience great, uncontrollable urge to know the value of pi. How can you get the value of Pi with relative accuracy? Assume you are at a beach so you can draw whatever you want with the stick."

A:

First off, thanks veraergertschuh [http://veraergertschuh.tumblr.com/post/113757364859/special-pi-day] and  huliia [http://huliia.tumblr.com/post/113648522466] for participating! Your use of coconut fiber is not far-fetched at all. When this riddle was thrown at me I immediately thought of rolling the coconut to get the circumference, but on a SANDY surface? Yeah right.

Using the idea that Pi is "how many diameters of a circle can you fit into its circumference" is the right idea. This method should give you a pretty good estimation of Pi, so I am very glad you guys saw my post and decided to participate! 

This should be a quick and dirty way to remind your brain the value of pi, and probably more realistic if you might faint soon.

Now here is the not-so-quick-and-dirty way. It still uses a similar idea of using relationships to get Pi.

Assuming your stick is nice and straight, against all odds of you reaching an unconscious state due to internal hemorrhage from your head trauma, you draw a diagram as shown below. 

Next, use the coconut to figure out how any coconuts can fit into the diagram. You carefully create EVEN grooves using the coconut to mark the coconut-count as your vision begins to blur and your body temperature rises to a point of heat stroke from the heat.

Now here is the fun part. The coconut number represents the area of each shapes. And the ratio from square to its circle is quarter of Pi! Watch:

[sasharypants]

Inception.

I don't think it gets more Inception than this.