Kids Rule

Slide Rules For Kids . . .   site under construction
NOTE TO PARENTS - Most of the content within the  "Kid's Rule"  pages, although designed for teaching kids ages 8 and older, will likely require interpretation by parent or teacher.
  Some images and documents
  Some example problems ( 3 )
  Calculus - easy, and fun!
  Virtual slide rule ( use with browser )
  Virtual slide rule ( Windows applications )
  Making the slide rule - overview
  Future plans

Some images and documents
1.) The slide rules in the various pictures and documents below may look really large, but they are in reality only about 10" long.

2.) When you open one of the images in your browser, the browser will likely shrink the image to fit your screen, causing all the scale markings to become distorted. The image can be restored to it's correct size in most browsers by right-clicking the mouse on the image and select the menu option to zoom, or just hold the mouse over the image and a + icon appears allowing a single click of the mouse to zoom to full size.

A picture of a "Kid's Rule!" slide rule made for a child Sophia Rule Front
A picture of a "Kid's Rule!" slide rule made for a parent Joe Rule Front
A slide rule in PDF format that you can print out. Because of PDF formatting, you must print it to standard 8.5x11" paper or it will not be printed the correct size as intended. AnyKid.pdf
The manual in PDF format - poor quality, but readable. The printed manual is much better. The printed manual distributed with a slide rule, is not a printout of the PDF, but rather the PDF is a collection of screenshots of the manual, which is then converted to PDF format for use on the WEB. KidsRuleManual.pdf
A few pictures of a slide rule made for someone who is a collector, enthuisiast, and teacher.
note: The slide rule shown has a glass cursor which is available for teachers and parents ONLY. Cursors of plexiglass are the type available for kids.
Slide Rule Front
Slide Rule Slide Zoom
Slide Rule Back
A couple of pictures of new CI scale added.
note: Shows slide rule prior to cutting to shape - cursor is just layed on it for picture
Slide Rule With CI Scale
Slide Rule With CI Zoom

Some example problems follow
If this is the first time you'll be using the slide rule, please pay very close attention, work slowly, and please do not allow yourself to feel intimidated by all the tiny lines and numbers. The slide rule is very simple to use! Once you learn how to do just a few problems, everything will begin to make sense.

Example slide rule problem #1
* The example below cannot be used by those participating in the free slide rule giveaway
* Special note: you can use a  virtual slide rule  to practice on
If 5 candy bars cost $3, how much for 4 candy bars?
Answer: $2.40
Solution: put C5 over D3 and find D6 below C1, then see D240 under C4

C5 = 5 candy bars
D3 = $3.00 for the 5 candy bars
C1 = index showing $.60 as price per candy bar
D240 below C4 = $2.40 for 4 candy bars

Then without moving the slide:
D12 below C2 shows 2 candy bars cost $1.20
D54 below C9 shows 9 candy bars cost $5.40
D36 below C6 shows 6 candy bars cost $3.60
      click image below to expand
      The example image linked to below is rather large.
      You may need to tell your browser to show it full size after it loads.
 D15 below C25 shows that for $1.50 you'll only get 2.5 (2-1/2) bars - the cashier gets the other half I suppose.

What's going on in this problem?
Placing C5 over D3, divides 3 by $5.00. The answer to that problem, $.60 can then be found below C1. The C1 is often referred to as an index, and is used frequently in problems such as this. After placing the slide rule in that position, a "table" of relationships of the same ratio is created. In the example above, we then try to find how much 4 candy bars would cost, and the only requirement is to simply look under the 4 where we find the value, $2.40.

If you think about what just happened, you may then realize that to find out a price for any amount of candy bars with this relationship between price and quantity, all that is required is to look under the quantity to find the price. Did you notice how simple this type of math is to do on the slide rule? With a hand-held calculator, this problem would have required a lot of pressing of the buttons to get many answers.

Now, try it on a virtual slide rule   

Example slide rule problem #2
* The example below cannot be used by those participating in the free slide rule giveaway
You can do addition by multiplying and dividing on the "Kids Rule!" slide rule, but you will need to be able to add 1 to any number in your head for this to work.

The formula is (A/B + 1) x B = answer.

  add:         10 + 5 = 15
  mult/div: (10/5 + 1) x 5 = 15

move the slide right, putting C5 over D10 and find D2 below C1, then add 1 in your head, making the 2 a 3. Move the slider left until C1 is over D3. Finally, read the answer of D15 below C5

What's going on in this problem?
Placing C5 over D10, divides 10 by 5. The answer to that problem, 2 can then be found below C1. As mentioned in the previous problem, C1 is often referred to as an index, and is used frequently in problems such as this. Now we have the answer to the first part of the problem. Next we add the 1 in our head to get 3. The next thing in the formula is to multiply the 3 by 5, so we place our index, C1 over D3 and look for the answer below C5, which turns out to be 15, as promised!

Now, try it on a virtual slide rule

I'll return to this example with pictures of the settings on the slide rule to perform the task, just as in the first example.

Example slide rule problem #3
* The example below cannot be used by those participating in the free slide rule giveaway
You can multiply 3 numbers with a single move of the slide on the "Kids Rule!" slide rule.

The formula is:
1.) CI-1st number to multiply, goes over top D-2nd number to multiply.
2.) pick any C-3rd number, and final answer is below on D.

 multiply:         5 x 3 x 4 = 60

move the slide right, putting CI5 over D3, below C1 you'll see D15 - an intermediate answer. Move the cursor to C4 and below it find the final answer C60

What's going on in this problem?
Placing CI5 over D3, sets the slide rule to multiply, using the "inverted" scale. The answer to a multiplication of this form is then found below C1

Then without moving the slide:
D9 below C6 shows 5 x 3 x 6 = 90
D45 below C3 shows 5 x 3 x 3 = 45
D75 below C5 shows 5 x 3 x 5 = 75
also notice:
D9 below C6 shows 25 x 6 x 6 = 900
D45 below C3 shows 75 x 2 x 3 = 450
D75 below C5 shows 2 x 75 x 5 = 750

Now, try it on a virtual slide rule

I'll return to this example with pictures of the settings on the slide rule to perform the task, just as in the first example.

Making the slide rule - overview
 The scales
Due to the placement of the lines - using logarithmic scaling - it would be extremely difficult to make something like this using image-editing software. To make these rules, I wrote code, that creates the PDF, using the  C programming Language.  The code creates a PDF file (the one linked to above) using a postscript format. The postscript format allows data points to be sent directly to a printer, which as some people may know has a very high DPI (Dot-Per-Inch) capability. To understand this better, a 15" video monitor capable of a maximum screen resolution of 1280x1024 would most likely have a DPI of about 85 - compare that to a typical printer these days which has about 600. However, when referring to computer monitors, the terminology "Pixels Per Inch" is usually used. The high DPI of a printer makes it one of the best formats for what is often referred to as "line art". A video monitor displays images using raster graphics image often known as "bitmap". Even though the image on your screen may look very crisp, when examined under magnification the spacing between groups of dots (pixels) becomes very obvious. Because of that spacing, even the highest resolution, widest screen would require a great deal of scrolling to create scales such as these.

Some of this talk about the printer resolution versus the monitor resolution can be best understood by opening the slide rule PDF linked to above. If you open that PDF and zoom to 100%, the slide rule will look HUGE. That's because the PDF viewer is adjusting things to fit your monitor, while still maintaining the "programmed" distance between lines, which quite literally takes a whole lot more space. If you zoom it back until the entire slide rule fits within the boundaries of your computer monitor, you'll see the lines of the scales all distorted as they are all crammed into the limited dots available on your video monitor. Finally, If you print the PDF to a typical printer with at least 600 dpi and a selected paper size of 8.5x11", it will only be about 10" long while on your PC monitor, if zoomed to 100% as mentioned above, you will have to keep scrolling since it may be over 50" long.

 The cursor
The cursor shown in the   MarkSlideZoom.jpg  image above is one I cut from a plate of glass. The edges were then ground and finally sanded for a nice finished look. The cursor lines were etched into the back using a carbide scribe that I created. The lines are a little wider than .001" and are cut into the glass about half again that distance. The lines are then filled with a deep red dye based ink. Due to the fine line, a pigmented ink (or paint) could not be used since the line is finer than many pigments. The glass lens is attached to plastic sliders which fit into grooves cut into the slide rule body.

 The back plate
The backplate is an option and can be made from various woods. The backplate shown in the  MarkSlideBack.jpg  image above is made from oak.

Future plans
I'm really getting excited about making this whole thing out of aluminum. I'm still undecided about all the issues involved. I'd likely screenprint the scales on the aluminum on some, and router them in on others. The screenprinting becomes complicated when multiple colors are introduced - and the "Kids Rule!" is very colorful, and I plan to keep it that way! I have already made up a screen for the scales, and the print from it it turned out almost as good as the scales on the slide rules presented here, so that shouldn't be much of an issue. The scales require a very fine screen mesh, but the fine mesh also takes a thinner ink, which, as with an inkjet printer, can actually create a higher quality result than a laser-jet because of ink flow between dots.

I'm thinking about making a decal of all the non-scale material for the aluminum rules which would overlay the rest of the rule. I can do the routered one about the same. I'd be using a revolutionary new aluminum composite material. It has a plastic sandwiched between two very thin sheets of aluminum. It's about 1/3 the weight of the aluminum used for a Pickett slide rule. The overall thickness is only 0.1". If I connect the upper and lower body like a Pickett, that would be the final thickness, and would of course allow me to add scales on the backside. If I add a back instead of the body connectors, then it would still be less than a quarter inch thick. The aluminum comes in many colors. The plastic middle is black. If you have an imagination, you may be able to see this as a very good scenario. I could router the ticks and numerics through the .001" inch of white aluminum revealing the black below, which would give the same appearance of the old K&E style rules. I could write code to translate my existing C code into the G-Code used by my CNC router. An alternative to the screenprinting of the scales is to tear into one of the inkjet printers and replace the roller with a feed table and just print them that way.

Even further down the road is a really high-tech type which uses an embedded system with miniature video monitor to track all movement of the slide of the rule to produce results at resolutions rivaling, or perhaps even superior to modern hand-held calculators. Such a rule may even include graphing capability. Imagine that - a marriage of analog and digital in the world of calculators... the best of both worlds!

I'm a "jack of many trades" with talents - applicable to this type of project - in woodworking, glasswork, metalwork, silkscreen, electronics, kung-fu, embedded system programming as well as many types of programming languages, and most of all I have a wild imagination and enough creativity to bamboozle my way through this kind of project. Okay, so I'm kidding about the kung-fu  :-)

That's right! Simple calculus can be performed on the "Kid's Rule!" slide-rule.

Most calculus can be very complicated, but some can be very easy. Almost all calculus (even the easy stuff) looks much more complicated than it is. Part of the reason it can look complicated is because it uses symbols and letters that you aren't used to seeing in math.

I'll show you how to do something using calculus known as, "integration". It will look very scary at first, mostly because of, as mentioned above, there will be symbols and letters used in the math that you aren't familar with.

One example I'll show, is how to find the area below an x^2 curve between 1 and 4, using only the C/D scale, and requiring only one move of the slide! Don't worry, I'll even explain what x^2 means, for those of you who are already looking puzzled by that.

Things aren't quite ready yet, but you can have a sneak-peek by clicking on this link.

Window App
That's right! A virtual slide rule for Windows 98/2k/XP/Vista

Some may have played around with the virtual Kid's Rule! slide rules  elsewhere  at this website - now you can get something even better to run on your PC. The windows application, unlike the browser based one, allows you to enter values for any of the boxes. It even contains a handy note-keeper pad so you can keep notes of your progress working with the slide rule, or just jot down notes, or cut and paste from other resources.

There is a free   demo application  available, as well as the  complete application,  which can be downloaded for $8.00. It's important to note the required 1280 wide screen resolution. The demo app is a good way to try everything with your system before considering the $8.00 purchase of the full application.

A special thanks to  TheSlideRuler.Org  for involvement in this project!