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As a secondary teacher in an underfunded district, I get paid very little money for the time and energy I put in to my teaching. I am totally cool with this, I never got into teaching for money, I enjoy a minimalist life style. However, there are certain implements that are very well suited to instructional goals but cost a decent amount of money and therefore I always drag my feet to spend the money (whether the school's or my own) to purchase these implements. I have been able to manage some hacks that I have found to be very useful in my classroom that cost little to no money to create. They include:

  • using jelly beans and toothpicks instead of the heavy duty plastic sticks (we call them D-sticks, not sure if that is an official name or what) to create geometric solids and/or molecular structures
  • Using webcam hardware/software on a laptop and a projector instead of having to purchase a $1000+ document camera (just have to make sure the software supports inverting the video image or else everything displays backwards)
  • Using old folders for lots of uses including double sided straight edges of arbitrary width, rulers using printouts like this, backing for using nets to build geometric solids, framing for student work, etc.
  • Buying sidewalk chalk and a plastic chalk holder (about 12 bucks for a pack of 20 sticks and two holders) instead of the pitiful chalk my school buys. Sidewalk chalk doesn't break, the holder keeps you hand from getting dusty, they write nice, fat characters that are readable even from the back of the room, they last forever (I have been using the same piece for over two months)

What are some other DIY/hack things that you all have done to create an implement/demo/etc that has been effective for instruction?

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    $\begingroup$ Does your school have clear transparencies (for old-school overhead projectors) lying around? These have many uses in a geometry classroom. I print protractors and rulers onto the transparencies and cut them out for students who don't have rulers/protractors at home. You can also print graphs and/or shapes onto them to illustrate congruency, rigid transformations, tessellations, corresponding sides and angles, complementary/supplementary angles, etc by overlaying the transparent version onto a hard-copy worksheet. (Just a comment for now until I get around to pulling examples.) $\endgroup$ – Xi Yu Apr 2 '15 at 19:58
  • $\begingroup$ jelly beans and toothpicks. I gotta try this. +1 $\endgroup$ – James S. Cook Aug 6 '15 at 16:07
  • $\begingroup$ I found Gummy Bears and toothpicks work better than jelly beans and toothpicks. My students had trouble sticking toothpicks into jelly beans. I used colored toothpicks which delighted everyone. $\endgroup$ – Amy B Aug 6 '15 at 20:21
  • $\begingroup$ @AmyB yes i have also had trouble with jelly beans, especially the standard smaller sized ones such as Jelly Bellys. However, if you can find the larger sized jelly beans (usually store brand) they hold the tooth picks very securely. I really like the gummy bear idea too :) $\endgroup$ – celeriko Aug 6 '15 at 20:58
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Circle generators: disposable cups, you can trace around the rim and the base for quick circles.

Patty paper is pretty cheap and totally worth it not just for constructions, but as tracing paper for all kinds of purposes. http://www.amazon.com/Geometry-Patty-Paper-Sheets-Single/dp/B001OMEGFS Can be an equivalent measurement tool to a compass sometimes.

"Compass": paperclip and two pencils will work in a pinch. You can bend it to adjust the radius slightly. Fix one pen in one loop and swing the other pen around in the other loop. See http://www.ictm.org/journal/index.php/imt/article/view/68/66

GeoGebra and Desmos (both free) can replace graphing calculators entirely (and do more). You'll need either computers, tablets, or phones. I found 2 students to 1 device works well, maybe even better than 1:1. www.geogebra.org www.desmos.com

This one isn't cheap, but it is cheaper: You can use a Microsoft Surface and a normal projector and OneNote/Powerpoint as a "Smart Board". Note: this is much better than a iPad in two big ways: One, the pen is a separate input from your finger, so more accurate and you can interface with pen and finger. Two, the Surface is a full laptop, in addition to a tablet, so it can run any windows program. There are other tablets that can do this as well-- I just have had good experiences with the Surface. If you're going to buy a laptop for yourself anyway, make it a Surface and you can handwrite and draw. You can also go wireless drawing with some creative shenanigans. a pic to illustrate: http://i.imgur.com/To4VgKM.png Surface also can be used as a DocCam.

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I've mentioned the expensive polydrons before, but in fact one can go far in exploring polyhedra (e.g., Euler's $V-E+F=2$) via paper cutouts, which only require the ability to print & copy & scissors & a bit of glue or tape. For example, see the website www.korthalsaltes.com. Note the templates even include the gluing tabs.


         
          DodecaColor3D


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    $\begingroup$ Also good for polyhedra are drinking straws. You can join them together with plasticine, or use the little plastic ring that comes off the lid of a plastic milk bottle. $\endgroup$ – DavidButlerUofA Aug 7 '15 at 1:17
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    $\begingroup$ Another way to make dodecahedra - out of post-it notes - youtu.be/vjOOhemquss . They were great fun for when I started group theory $\endgroup$ – Bysshed Aug 15 '15 at 19:22

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