Stephen Hawking – Understanding the Universe

Pi Day is a day math and science enthusiasts love, not only for all the fun Pi Day activities, but also because it was Albert Einstein’s birthday, one of the most iconic mathematicians/scientists/physicists, who developed the theory of relativity. This year’s Pi Day, ironically, the world lost another renowned physicist, Stephen Hawking. Whether you never heard of Stephen Hawking until the movie The Theory of Everything (2014) or whether you only know him from his voice on the Simpsons or Star Trek, The Next Generation or The Big Bang Theory, his death is a loss to the world of science and math.

It seems silly for me to list all that Mr. Hawking contributed, when his website does such a terrific job of that already. Here is the link to his site, where you can read about Stephen Hawking, see the many publications of his, the books he wrote, the lectures he gave (transcripts), the movies about him and with him, and videos he made. This is a great resource for teachers and students to explore.

I want to leave you with a video of Stephen Hawking talking about his love of science and as he said “I did my work because I wanted to understand the universe”.

Rest in Peace and thank you for all your contributions that have helped the rest of us understand our universe a little better.



Applying Prior Knowledge Is About Precise Mathematical Language

In the course I am currently teaching at Drexel University, we have been focused on the importance of addition and multiplication properties as students progress through mathematics. Particularly the idea of inverse numbers (additive inverses and multiplicative inverses),the additive and multiplicative identities, and the commutative and associative properties of addition and multiplication. A strong foundation in these concepts, which starts in elementary school and builds as students progress to more abstract and complex math concepts such as proportional reasoning, solving equations, composition of functions, and working with matrices, is really important. In fact, if we spent more time using precise language and justifying our reasoning with properties consistently, as we model and help students learn and discover, there would be a lot less confusion and much more connection of prior knowledge to ‘new’ concepts. Instead, we often provide a short-cut, or a ‘trick’ (with a cute acronym like KSP (keep, switch, flip) or ‘Cross-multiply-divide’ with no basis in the true mathematics. Students focus on memorizing isolated rules versus connecting new concepts and seeing learning as just an extension of prior knowledge.

Let me try to explain what I mean by providing a sense of prior knowledge and how it connects to more abstract concepts:

Prior knowledge:

  • Additive identity: 0 and the Additive Identity Property:  a + 0 = a (5th/6th grade)
  • Additive inverses create the additive identity – so -b + b = 0 or -c + c = 0 (5th/6th grade)
  • Multiplicative identity: 1 and the Multiplicative Identity Property: b*1=b or 1*b=b (5th/6th grade)
  • Multiplicative inverses create the multiplicative identity (i.e. a 1) = d * 1/d = 1 or -1/f *-f = 1 (5th/6th grade)
  • Addition and multiplication are commutative (switch the order and you get the same solution) (1st/2nd grade) and associative (switch the grouping and you get the same solution) (3rd grade)(this explains why we want to change subtraction to addition of the additive inverse number, and why we change division to multiplication of the multiplicative inverse (reciprocal) – so we can USE THE PROPERTIES!!!

Understanding the above, then makes solving equations easier – and we don’t need to avoid equations with fractions or decimals, because the properties apply to these rational numbers as well.

Example:  -5 = (1/3) x – 8

  1. Change the problem to addition of the additive inverse: -5 = (1/3)x + (-8)
  2. Add 8 to both sides (commutative property – can add in any order) because adding additive inverses (8 and -8) make zero (additive identity property)  -5 + 8 = (1/3)x + (-8) + 8
  3.  Group the inverses (associative property) and solve:  -5 + 8 = (1/3)x + (-8 + 8) which is equivalent to 3 = (1/3)x + 0  equivalent to 3 = (1/3)x
  4. Use the multiplicative inverse property (multiplying by the reciprocal will create a 1) and multiply by 3/1 on both sides:  (3/1)*3 = (3/1) *(1/3)x (commutative property allows us to multiply in either order on both sides).
  5. The multiplicative identity property says 1 times any number is itself, so we end up with 9/1 = 1 *x or 9 = x

*Note – we did not use subtraction or division at all – we used the understanding of inverses, identities, and addition/multiplication properties to explain. No tricks, and working with actual numbers (so fractions and integers) with justification for all steps.

Example: Solve the proportion  3/16 = x/20

  1. This is really an equation where the quantity x is being multiplied by 1/20. Understanding that I can use the multiplicative inverse to multiply by the reciprocal to make a 1, I multiply both sides by 20/1:
    • 20/1 * 11/12 = x/20 * 20/1 (commutative property lets me multiply in either order on both sides)
    • I can even decompose my multiplication and think about making ones through the same understanding: 4*5*3 /4*4= 1*x
    • 15/4 = x/1 or x = 3.75 (multiplicative identity)
  2. Note – the trick we often tell students to memorize is ‘cross-multiply and divide’, but if instead we focused on just applying their understanding of multiplicative inverse and making those 1 pairs, there would be less confusion, less forgetting the ‘trick’, and less applying that trick to other problems where it is in appropriate. 

Obviously I can’t demonstrate a whole course of study in one blog post – what I am really emphasizing here is how important consistent mathematical vocabulary and use of properties is, instead of acronyms, short-cuts, tricks, mnemonics, etc. that we often give students with no basis in understanding. Instead of seeing math as a connected whole, building on to prior knowledge as they move through the grades and topics, we treat it as isolated topics with no connection. It’s no wonder students think every year they are learning something new. If last year when they worked with division of fractions their teacher taught them to “Keep, Change, Flip”, and this year the teacher is talking about Ketchup Covers Fries or KSF….no wonder they are confused. None of these are grounded in the properties and vocabulary of mathematics.

What we should be doing instead is focus on applying properties and using the mathematical language/vocabulary/properties right from the very beginning and ALL THE TIME. So instead of disconnected acronyms of KSF or KCF,  they focus on extending their understanding of additive inverse, inverse operations with the inverse number and division of fractions ends up being just an extension of what they did with subtraction of integers – i.e. use your inverse operation with the inverse number. So dividing with rational numbers is just multiplication (inverse operation) by the multiplicative inverse (i.e. reciprocal), similar to subtraction being addition (inverse operations) with the additive inverse (opposite signed number) – same general idea, same vocabulary, and just building on prior knowledge.

Let’s stop dumbing down mathematics and use the words and properties that truly allow students to connect and look for those patterns and develop their own understandings and rules. Let’s get away from tricks and mnemonics as our ‘teaching’ method – instead, let students figure that out themselves through the use of precise math language and application of properties. Let’s start in elementary school. Use precise mathematical language (along with clarifying words of course, but always with (not instead of) proper mathematical language/vocabulary/properties).

Think about it – we wouldn’t change the Spanish word for grandmother (abuela) or the French word for bread (pain) to other words, because then how would we communicate and be understood by others speaking those languages? Why is it okay to change the words or use different words or tricks, instead of the using the math language and properties? No wonder students are often so confused or why teachers think they have to ‘reteach’ things every year – if we are not consistent with students in using mathematical language, we are in fact talking a different language to them. No wonder they so often seem lost and frustrated.

Casio Scientific Calculator QR Code – The Power of Visualization

I was recently asked on my YouTube video channel if Casio’s graphing calculators also have QR code capabilities like the Casio FX991 ClassWiz Scientific Calculator. It was a great question – and my response was the graphing calculators don’t need that QR code because they already have the power of visualization. The purpose of a QR (Quick Response) code is to get information quickly, whether that’s an audio or a visual or data (usually on your mobile device). With graphing calculators, that is part of the calculator – we can enter data in many forms and see multiple representations of that data very quickly – a graph, a table, a function, specific points, etc.within the graphing calculator itself, making a QR code unnecessary. And, if you are using the graphing software/emulators, you can put these graphs and multiple representations up very quickly.

Why does the Classwiz then have a QR code? This is a scientific calculator, which is incredibly inexpensive (from $15-19), so what’s the reasoning behind including QR code capabilities? The answer – to add the power of visualization and make this calculator have ‘graphing’ capabilities at a fraction of the cost. You can enter data in the form of functions, tables, spreadsheets, and then have the ability to see graphical representations of this data with the QR code.

Here’s a short video that talks about the differences in the graphing calculator versus the scientific calculator and demonstrates the QR code. You will also see a comparison of the tables and graphs represented on both calculators.

Creativity of Students – Provide Opportunities for Expression

I was straightening up my office – something I realized I do not do enough. I found a file of student projects from when I was teaching Geometry over 15 years ago. We had done some geometry poems for Valentines day – i.e. write a poem that utilizes mathematics vocabulary (getting that ELA and creativity flowing in my students), and I had clearly saved a few of my favorites.  There were other files of student projects – scale drawings of bedrooms and furniture (so students could ‘rearrange’ their rooms using a scale model), dilation pictures, transformation sketches from Sketchpad, problem-solving portfolios, and designing an aerial view of a city using geometric shapes and properties. As I walked through memory lane, looking at student work from years ago and remembering specific students, it really made me miss those classroom experiences. And what I had forgotten is how incredibly creative and thoughtful students are when given the chance to express themselves – you learn so much about them if you let them, what they know about mathematics, what they think, and what they don’t know if you provide opportunities to approach mathematics creatively.

I’d completely forgotten about the problem-solving portfolios I did with both middle and high school students in all my courses. They were given a choice of problems connected in some way to the math content we were learning or applications of prior knowledge, etc., and they were to choose from several. They had to complete one per unit and put it in their portfolio as examples of their problem-solving and learning/application of mathematics. This was way before the ‘Common Core’, but as I look at my expectations, it was very Common Core like. The idea behind was really very much centered around helping students to persevere and think critically about problems, use problem-solving strategies, and explain their interpretation of a problem, plan out a solution path, justifying their thinking, and showing multiple ways to approach a problem, and analyze their solutions to see if they made sense.  Here are the ‘steps’ they needed to go through and demonstrate in their problem-solving:

  1. Restate the problem in your own words, writing out any questions or wondering you have about the problem.
  2. Create a solution plan – what do you think about the problem  and why (is it hard, easy, does it seem similar to something you have seen or done before), what math might be needed, what problem-solving approach will you start with and why do you think this might be a good approach? What do you think might be the solution, before you begin?
  3. Work through the problem – include everything, especially if you changed your original plan and why. Write down everything that comes to mind and what you did to think through things.
  4. What is your solution and why do you think this is a reasonable solution?
  5. Analysis of your problem solving – What did you think of the problem after working through it? What did you learn from doing the problem, either about yourself or about math, or both!?

In reading through some of these (I’ve posted some samples below from several different portfolios), you can ‘hear’ students personalities coming out, you can immediately see if they might have a misconception about what the problem is asking or an interesting approach to a solution, or identify those who really needed some extra support because their art work was more substantial then their mathematical work! It gives great insight into who might need some extra support or who might warrant some extra challenges. But mostly – the freedom to choose, think on their own and be creative and work through their problems provided students and ability to express their learning in a different way than an answer on a test. I remember at the time I was considered a rather eccentric MS/HS teacher because I did all these ‘strange’ things like keep math portfolios and journals, use manipulatives, used technology (Sketchpad) and projects instead of tests to demonstrate learning. But – in looking back on the past, and looking at what we want from students today in mathematics, with College and Career Ready Standards and Mathematical Practices, I think it’s the right path. Provide students opportunities to think, choose, be creative, find multiple solutions, justify their answers and question their results. It brings out their creativity and they learn to express themselves as mathematicians.


Geometry and the Holidays

The holidays are upon us, so of course it makes complete sense to look for geometrical connections. Or maybe that’s just me?

As a geometry teacher (just finishing up a Geometry & Spatial Reasoning course), I am seeing geometry connections everywhere. From the wrapped presents, to the origami ornaments, to the snowflake patterns, I am constantly looking for those real-world connections and easy (and cheap), ways to get students working hands-on with math.

We are all familiar with ‘holiday math’ problems that connect to wrapping presents – i.e. how much wrapping paper do you need, how much ribbon, etc. Area, surface area, linear length connections all very obvious. But, as a geometry teacher, I am also curious about the gift boxes themselves. I know it is often difficult to find 3D models for learning, so boxes provide a cheap way to provide students hands-on explorations of nets, area, surface area, volume. So – teachers – get your students to bring in boxes after the holidays – so much you can do with these!!

Another thought – origami. This time of year, teachers often create holiday decorations with their students with paper-folding, which is fun, obviously, but can also be a great way to apply many math concepts. Shapes, fractions, and transformations for example. Take the following two origami designs – a star and a tree. As you are folding, you could be having students think about the individual shapes, but also the dimensions, the fractional parts after making a fold, what types of transformation have occurred – even congruence and corresponding parts.


For example, in the star above, after folds #1, what fraction of the square does each smaller square represent? When we fold that triangle in #2, what type of triangle is it? What fraction of the original square is represented in that yellow triangle?  What type of transformation does each fold represent? Are the triangles in #3 and #4 congruent? How do you know?

images (1)step-step-instructions-how-to-make-origami-christmas-tree-illustration-67138886

Again, looking at the tree folding above, what shapes do you see in #1? What fraction of the whole paper is each shape (so squares and triangles)? How about in #2? And which shapes are congruent? How do you know? Lots of great math, that you could really explore with students while they are also doing a fun hands-on activity.

Hopefully you can use some of these ideas with your students. Have a wonderful holiday season!!

Financial App (Pt 3 in series) – Let’s Talk About Money

pexels-photo-164501With the holiday season upon us, and people often spending beyond their means, it seems appropriate to continue the CG50 (and all Casio Graphing calculators) app exploration with the Financial App.

One thing we do not spend enough time on in K-12 education is financial literacy. I know there are some states that are trying to address this, but it is not enough. This lack of understanding about money, savings, taxes, interest, debt, etc. is a huge contributor to our enormous debt crisis. Take our current political focus on the ‘tax reform’ bill that’s up for a vote soon – most people do not understand the ramifications of this because they don’t really understand anything about finances and how taxes work. We do not in this country teach the basics of financial literacy, which is why we have so many people drowning in debt, losing their homes, barely surviving month-to-month on what they make, and forget about having the ability to save for the future. How many students really understand about saving money? Or how taxes impact their hourly wages (i.e. $10/hour is not that great when you factor in all the taxes taken out)? Or how not paying of your credit card monthly can make that $300 dollar purchase become a $400 or $500 dollar purchase?

When I taught in Virginia, they started a Personal Finance course ‘elective’ (only for stock-photo-working-coffee-phone-work-check-budget-finances-personal-finance-e841754e-765d-426e-af94-4b6a4ce9891fthose students technically not on the college prep track – which was silly, as ALL students should take a course on Personal Finance). I was lucky enough to be the pilot teacher in my school, so I could pretty much create the course. My goal was to help students understand the importance of financial planning so they could survive and thrive in the world, no matter where their path took them. We started with learning about different career options they were thinking of, and what a typical annual salary might be (so plumber, electrician, hair dresser, doctor, lawyer, teacher, etc). They learned to fill out job applications, and write resumes, and then we ‘pretended’ they had been hired and were receiving biweekly payments (I actually gave them ‘checks’). We learned about payments, investing, taxes, rent, credit cards, insurance, amortization,balancing a check book (the class had a ‘bank’), etc. They had to determine where they would live, whether they would get a car, how much they could spend on food, entertainment, etc. based on their salary. What they quickly learned is that their wages, after taxes, were often NOT enough to do much else – no fancy apartment and having to make tough choices (i.e. gas or food, no car, no expensive smartphone, taking bus, walking, no movies every week, no fast food, etc.) When a student comes to you all excited about their $9/hr job and all the things they will buy, and then realize after their first paycheck that it’s going to take months to have enough, it’s eye opening. And scary.

pexels-photo-164527What I learned is that we do not talk to students about real-world, practical mathematics enough –  simple things like saving money, calculating tips, balancing a checkbook, interest, credit card debt, etc. This is math they need in their everyday life. This is math that has purpose. This is math that will help them make smarter decisions about their future. Maybe if we did, we wouldn’t have so many people struggling to survive or believing every unrealistic promise they hear in the news..

My message – let’s get some Financial Literacy into K-12 mathematics programs!

With that said, here is a quick video on the Financial App that is available on the Casio graphing calculators. This video uses the CG50.

Graphing How-To – Hyperbola & Asymptotes on the CG50 Prizm

I realized I haven’t posted a ‘how-to’ video in a while, and, with this being the end of summer, there might be some students and/or teachers out there trying to learn some new skills before the school year starts up, hence this post. Why hyperbolas? No reason other than it helps highlight the Conics menu and I love the way it looks! My plan is to try to do some more how-to’s on a monthly or bi-weekly basis, especially as school starts up, so if there is a specific topic you want to explore, please let me know, as well as a specific Casio Calculator. There are several how-to videos out there already on my YouTube channel and Casio’s YouTube Channel, but if you have a specific content/calculator in mind, I will do my best!

The video below models one of the problems in our free Quick Start Guide for the CG50 (our newest version of our colored graphing calculator) on how to graph a conic section, in this case a hyperbola, using its equation, and then from that, finding its asymptotes, coordinates of the vertex, and the coordinates of the foci. This will be a nice example of how to use the Conic Menu option on the CG50 graphing calculator as well as our other graphing calculators, since the steps are the same.


Problem: Construct the graph of the conic section given by this equation: . Once graphed, find the asymptotes, the coordinates of the vertices and the coordinates of the foci.