Desmos: Percent Models


For the past 3 years, my district has offered a back to school PD summit.  Various people from inside and outside the district present. Since I’m Instructional Tech TOA, I presented. My sessions focused on Desmos and BreakoutEDU*.  The activity shared today was born out of a collaboration with one of my BreakoutEDU attendees, Candace.

She wanted to create a Breakout styled activity for a series of class openers. The questions were a mix of review problems, one topic being percents.  As I started working on the project, I felt strongly about building an interactive model that students could use when working on the percent problems.  A model that would strengthen their conceptual understanding of percents. A model that could be linked to the question set or class website allowing students to use it whenever needed.  I put the BreakoutEDU activity on hold while I went to work creating the Desmos AB.  This post discusses the result of my work.

*Side note:  I baked in a Desmos piece to the BreakoutEDU activity during the summer PD summit, but that’s for another post.

Percent Model – Activity Link

The Percent Model

The Activity Builder is sectioned into three groups where each group addresses one of the 3 types of percent questions, finding the part, finding the whole and finding the percent.

A:  Finding the Part  

The first screen, within a group, sets up the problem.


A: Finding the part

Screen 1 – Figure 1


A number line where 30% of 40 is shaded

Screen 1- Figure 2


Screen 2:

The second screen is designed to support student thinking.  Students can use the sketch tools to annotate the picture and test values.  In this example, a student divided the textured region into three sections in order to identify 10%.


Screen 2 – Figure 3


When 4 is entered into the answer box, an error message displayed.  Four is not the answer to the original question, however, this step confirms that 4 is in fact 10% of 40. This information can be used to calculate the actual answer, as shown in Figure 5. 


Screen 2- Figure 4


Screen 2- Figure 5


The graphics and student annotations carry over to the third screen in the grouping.  Students now reflect on their process and communicate their thinking to classmates and teacher.


Screen 3 – Figure 6


B:  Finding the Whole

The second grouping, Finding the Whole, works similarly to the first.  Students enter either teacher provided information or their own part and percent.  Then they determine the whole.  In this version, the animated bar needs to fill the entire rectangular section (as shown below). The final step is to explain their process.


Screen 6 – Figure 7


Screen 6 – Figure 8


C:  Finding the Percent

The last type, Finding the Percent, follows the same structure as the two previous.  Students enter in information, determine the answer and reflect.  The expected answer is a percent and students are asked to round their solution to the tenth position (Figure 10).


Screen 8 – Figure 9


Screen 8 – Figure 10


Classroom Uses

When developing this Activity Builder, I envisioned two different uses – Independent and Teacher guided. As mentioned in the Inspiration section, the original plan was to create a percent model for students to use when working through independent problems.  If percent problems are integrated into a spiral review like my colleague is doing, then placing the direct activity link on a class website gives students access to the model at any time needed.

You will find the activity link by first clicking on the 3 vertical dots in the upper right-hand corner and then clicking on Share activity.  This method takes students to the activity’s “home” screen (Figure 12).  They can open the activity two ways, either by clicking Student Preview or clicking on one of the displayed screens.


Figure 11


Figure 12


If using the model as a part of a lesson, then it’s best to create a class code.  It should be noted that class codes last a couple of weeks before archived.  Once students join the activity, teachers can use the conversation tools (Figure 13) to pace the screens depending on the desired intent.  For more information on the Anonymize, Pacing and Pausing features, click here.  I suggest preparing percent problems that naturally allow for various paths to a solution and then use the sketch and reflection screens to cultivate mathematical discourse.


Figure 13


About jgvadnais

Instructional Technology Coach. Desmos Fellow. Google Level 1 Certified. SoCal transplant. New Englander at heart. Lover of yoga, dogs, green smoothies and coffee creamer
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