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Video: How to draw an egg

Katie’s done another video! This time it’s a neat method for constructing an egg-shape, using arcs of circles.

Bonus challenge: See if you can count how many times Katie accidentally says ‘compass’ instead of ‘pair of compasses’ during the video.

Cutting an oval pizza – video

As if there wasn’t enough maths/pizza news lately, the story has hit the red-tops recently that UK supermarkets are scamming consumers by offering them oval-shaped pizzas – marketed in the high-end/’Extra Special’ ranges, with more expensive (sounding) ingredients like mozzarella di bufala, roquito peppers and merguez sausage, and a distinctive pair of artisanally different radii. These pizzas apparently cost more per gram, because their elliptical shape means they’re actually smaller than a circle with the same diameter. Cue plenty of ‘costing you dough’ and ‘cheesed off’ puns.

While we’re not massively bothered by the pricing, the articles do raise, and then completely fail to address, an interesting point: an oval pizza is harder to cut into equally sized pieces! Luckily, maths is here to save the day. I found a nice method and made a video explaining how it works:

Take a look and improve your future pizza cutting technique!

Video: The Aperiodical’s π approximation challenge

As part of our massive π day celebrations, The Aperiodical has challenged me with the task of assembling a group of mathematicians, some bits of cardboard and string, and a video camera, and attempting to determine the exact value of π, for your entertainment.

The challenge, which was to be completed without a calculator, involved using known mathematical formulae for π and its occurrence in the equations of certain physical systems. In the video below, seven different methods are used – some more effective than others…

If you reckon you too can ineptly compute a value in the region of π (in particular, if you can get a more accurate approximation than the date of π day itself, which gives 3.1415), feel free to join in the challenge and see how close you get.

Translate Numberphile, please / Traduisez Numberphile, s’il-vous-plaît / Bitte übersetzen Numberphile…

Numberphile is that cool YouTube channel with the videos about the numbers and the philes. You might remember them from the time they did that ace video about our integer sequence reviews. But if you’re unlucky enough not to understand the English as she is spoke, then that’s no use to you.

But it could be! Chief Numberphile Brady Haran has set up a page asking for translations of the videos, so everyone can enjoy them. As long as you’re fluent in one of the languages for which a video already has subtitles, the process is pretty simple: you download a caption file in one language, translate it into another, and upload it back to the site. And then you’ve done a good deed!

Brady’s just posted on Twitter that he’s already approved 24 translations since starting the project yesterday evening, so join your fellow Frenchmen/Flemings/Faroese and get translating. (I suggest you start with “Six Sequences”…)

Submit a translation: Translations for Numberphile at

via Brady Haran on Twitter

Amazing Sierpinski Tetrahedron

In the wake of a flurry of tetrices being constructed in schools all over the country (see this post about fractal Christmas tree worksheets, and this post featuring photos of completed trees), we’ve also been sent a video of a school group constructing an ambitious and impressive fractal structure, using envelopes cleverly folded into tetrahedra. The video is below, and features (eventually) a level 5 Sierpinski Tetrahedron, made from 1024 envelopes!

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Via teacher Tim Dolan on Twitter.

The Mathalicious weekly video series has launched

You may remember Math52, a Kickstarter project from Mathalicious which reached its goal in June. This promised, “every week for a year we’ll create a short video exploring a unique application of math in everyday life”. Now the Mathalicious video series has launched with two videos, both less than two minutes in length, available via YouTube.

The first video, Tip Jar, explores tipping in restaurants.

When we go out to eat at a restaurant, it’s customary to tip as a percent of the total bill. But is this fair? And what are some other ways we might pay waiters & waitresses?

The videos are snappy and nicely produced. The Mathalicious website offers free lesson plans and materials to support the video in the classroom.

YouTube channel: Mathalicious: the Video Series.