Animal Digits / Digit Sums
(Julia Robinson Mathematics Festival, 2020)
The number in each circle is the sum of the digits in all connected circles. Play around with your class – making simple patterns of connected circles and then trying to put numbers in them so everything adds up.
Here is the pdf from the presentation above.
I’m using the title “Digit Sums” when I’m giving this puzzle to the older students and “Animal Digits” for the younger students.
This puzzle is nearly as good for practicing algebra skills in grades 7-9 as it is for practicing digit addition in grades 2-3. To solve the first lion puzzle in the video – let’s put the value 10x+y in the central circle. That means the tens digit is x and the units digit is y. Let’s put the digit z in each of the three surrounding circles. We end up with two equations:
10*x + y = 3*z
x + y = z
Subtracting lets us get rid of the y…
9*x = 2*z
Which can only be satisfied by x=2 and y=9. I’ll leave it to you to figure out the rest. 😉
Teaching is an experimental science. Don’t expect to be a great teacher your first year standing in front of a class.
Standards for Mathematical Practice
MathPickle puzzle and game designs engage a wide spectrum of student abilities while targeting the following Standards for Mathematical Practice:
MP1 Toughen up!
Students develop grit and resiliency in the face of nasty, thorny problems. It is the most sought after skill for our students.
MP2 Think abstractly!
Students take problems and reformat them mathematically. This is helpful because mathematics lets them use powerful operations like addition.
MP3 Work together!
Students discuss their strategies to collaboratively solve a problem and identify missteps in a failed solution. MathPickle recommends pairing up students for all its puzzles.
MP4 Model reality!
Students create a model that mimics the real world. Discoveries made by manipulating the model often hint at something in the real world.
MP5 Use the right tools!
Students should use the right tools: 0-99 wall charts, graph paper, mathigon.org. etc.
MP6 Be precise!
Students learn to communicate using precise terminology. MathPickle encourages students not only to use the precise terms of others, but to invent and rigorously define their own terms.
MP7 Be observant!
Students learn to identify patterns. This is one of the things that the human brain does very well. We sometimes even identify patterns that don't really exist 😉
MP8 Be lazy!?!
Students learn to seek for shortcuts. Why would you want to add the numbers one through a hundred if you can find an easier way to do it?
Please use MathPickle in your classrooms. If you have improvements to make, please contact me. I'll give you credit and kudos 😉 For a free poster of MathPickle's ideas on elementary math education go here.
Gordon Hamilton
(MMath, PhD)
