Robert Kaplinsky
@robertkaplinsky.com
Math educator. Love helping teachers.
Open Middle co-founder. #OpenMiddleBook author. #ObserveMe creator. Grassroots Workshops President. Get lessons & ideas: http://bit.ly/rkupdates
Open Middle co-founder. #OpenMiddleBook author. #ObserveMe creator. Grassroots Workshops President. Get lessons & ideas: http://bit.ly/rkupdates
Did you know that many of the stores you shop at use mathematical modeling to make predictions about you? Read about how Target can predict which of its customers are pregnant and when the baby is due!
robertkaplinsky.com/math-mo...
robertkaplinsky.com/math-mo...
January 8, 2026 at 11:34 PM
Did you know that many of the stores you shop at use mathematical modeling to make predictions about you? Read about how Target can predict which of its customers are pregnant and when the baby is due!
robertkaplinsky.com/math-mo...
robertkaplinsky.com/math-mo...
How deeply do your students understand parallel and perpendicular lines if they can't create sets of points to define the lines? Try out these two Open Middle problems from Nanette Johnson:
www.openmiddle.com/perpendi...
www.openmiddle.com/parallel...
www.openmiddle.com/perpendi...
www.openmiddle.com/parallel...
January 8, 2026 at 1:10 AM
How deeply do your students understand parallel and perpendicular lines if they can't create sets of points to define the lines? Try out these two Open Middle problems from Nanette Johnson:
www.openmiddle.com/perpendi...
www.openmiddle.com/parallel...
www.openmiddle.com/perpendi...
www.openmiddle.com/parallel...
Attention high school math teachers! How do you measure distance on a circular road? This lesson provides a context for students to develop conceptual understanding of arc length.
robertkaplinsky.com/work/ho...
robertkaplinsky.com/work/ho...
January 7, 2026 at 11:14 PM
Attention high school math teachers! How do you measure distance on a circular road? This lesson provides a context for students to develop conceptual understanding of arc length.
robertkaplinsky.com/work/ho...
robertkaplinsky.com/work/ho...
Are your students learning about parallel lines and transversals? Try out these two Open Middle problems from Shelli Foust:
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
January 5, 2026 at 11:33 PM
Are your students learning about parallel lines and transversals? Try out these two Open Middle problems from Shelli Foust:
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
www.openmiddle.com/parallel...
Want to challenge your Geometry students to find the area of triangles? Try out this Open Middle problem from Dan Wulf. www.openmiddle.com/area-of-...
January 2, 2026 at 11:43 PM
Want to challenge your Geometry students to find the area of triangles? Try out this Open Middle problem from Dan Wulf. www.openmiddle.com/area-of-...
This lesson uses distances between freeway signs as a context for placing fractions on a number line and subtracting mixed numbers. Make sure to share it with any upper elementary teachers you know.
robertkaplinsky.com/work/fr...
robertkaplinsky.com/work/fr...
January 2, 2026 at 8:07 PM
This lesson uses distances between freeway signs as a context for placing fractions on a number line and subtracting mixed numbers. Make sure to share it with any upper elementary teachers you know.
robertkaplinsky.com/work/fr...
robertkaplinsky.com/work/fr...
When Febreze was introduced, people loved it but hardly used it because they didn't realize they needed it. Here's the fascinating story of why we don't notice what we're familiar with.
robertkaplinsky.com/febreze... #ObserveMe
robertkaplinsky.com/febreze... #ObserveMe
January 1, 2026 at 11:34 PM
When Febreze was introduced, people loved it but hardly used it because they didn't realize they needed it. Here's the fascinating story of why we don't notice what we're familiar with.
robertkaplinsky.com/febreze... #ObserveMe
robertkaplinsky.com/febreze... #ObserveMe
Here's a challenging Open Middle problem to help students develop conceptual understanding of quadratics in standard form: www.openmiddle.com/maximum-...
January 1, 2026 at 1:10 AM
Here's a challenging Open Middle problem to help students develop conceptual understanding of quadratics in standard form: www.openmiddle.com/maximum-...
This lesson will help students evaluate which factors affect profitability when making a lemonade stand. Can they earn enough money to make it worth the their time and effort?
robertkaplinsky.com/work/le...
robertkaplinsky.com/work/le...
December 31, 2025 at 11:14 PM
This lesson will help students evaluate which factors affect profitability when making a lemonade stand. Can they earn enough money to make it worth the their time and effort?
robertkaplinsky.com/work/le...
robertkaplinsky.com/work/le...
If your Geometry students are working on the midpoint formula, try out this Open Middle problem from Dane Ehlert with them. www.openmiddle.com/midpoint...
December 29, 2025 at 11:33 PM
If your Geometry students are working on the midpoint formula, try out this Open Middle problem from Dane Ehlert with them. www.openmiddle.com/midpoint...
Here's an idea for how you can get an extra month of time to teach students during the regular school year based on ideas from Matt Vaudrey.
robertkaplinsky.com/heres-c...
robertkaplinsky.com/heres-c...
December 29, 2025 at 5:03 PM
Here's an idea for how you can get an extra month of time to teach students during the regular school year based on ideas from Matt Vaudrey.
robertkaplinsky.com/heres-c...
robertkaplinsky.com/heres-c...
How can we figure out if we have enough paint for a handball wall? Use this problem with your students as a context for area.
robertkaplinsky.com/work/do...
robertkaplinsky.com/work/do...
December 29, 2025 at 12:13 AM
How can we figure out if we have enough paint for a handball wall? Use this problem with your students as a context for area.
robertkaplinsky.com/work/do...
robertkaplinsky.com/work/do...
If you're a presenter and want to avoid people thinking that you always say the same things, then you need to read this blog post:
robertkaplinsky.com/present...
robertkaplinsky.com/present...
December 28, 2025 at 1:13 AM
If you're a presenter and want to avoid people thinking that you always say the same things, then you need to read this blog post:
robertkaplinsky.com/present...
robertkaplinsky.com/present...
If you teach K-5, check out these 3-act tasks from Catherine Castillos. They're fun and engaging ideas to get kids making sense of math: mscastillosmath.wordpress.c...
December 27, 2025 at 8:07 PM
If you teach K-5, check out these 3-act tasks from Catherine Castillos. They're fun and engaging ideas to get kids making sense of math: mscastillosmath.wordpress.c...
Want students to practice applying math to real life, but wish you had something more engaging and meaningful than word problems? Then you should check out my recorded webinar with elementary, middle, and high school versions.
robertkaplinsky.com/webinar
robertkaplinsky.com/webinar
December 27, 2025 at 5:45 PM
Want students to practice applying math to real life, but wish you had something more engaging and meaningful than word problems? Then you should check out my recorded webinar with elementary, middle, and high school versions.
robertkaplinsky.com/webinar
robertkaplinsky.com/webinar
Are your students working on parallel and perpendicular lines? Try out these two Open Middle problems from Bryan Anderson:
www.openmiddle.com/equation...
www.openmiddle.com/equation...
www.openmiddle.com/equation...
www.openmiddle.com/equation...
December 26, 2025 at 11:43 PM
Are your students working on parallel and perpendicular lines? Try out these two Open Middle problems from Bryan Anderson:
www.openmiddle.com/equation...
www.openmiddle.com/equation...
www.openmiddle.com/equation...
www.openmiddle.com/equation...
As a young math geek in high school, I figured out the best way to win the grand prize at Chuck E. Cheese's when playing Skee Ball. Use this lesson to help elementary students decompose numbers. Or secondary students can use systems of equations.
robertkaplinsky.com/work/sk...
robertkaplinsky.com/work/sk...
December 26, 2025 at 8:07 PM
As a young math geek in high school, I figured out the best way to win the grand prize at Chuck E. Cheese's when playing Skee Ball. Use this lesson to help elementary students decompose numbers. Or secondary students can use systems of equations.
robertkaplinsky.com/work/sk...
robertkaplinsky.com/work/sk...
Wish your students would have more meaningful conversations when you asked them questions? Then check out this professional development activity you can use with your colleagues.
robertkaplinsky.com/questio...
robertkaplinsky.com/questio...
December 25, 2025 at 11:34 PM
Wish your students would have more meaningful conversations when you asked them questions? Then check out this professional development activity you can use with your colleagues.
robertkaplinsky.com/questio...
robertkaplinsky.com/questio...
Can your high school students create a parallelogram, triangle, or rectangle by listing their points when given one? Find out using these three Open Middle problem from Bryan Anderson.
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
December 25, 2025 at 1:10 AM
Can your high school students create a parallelogram, triangle, or rectangle by listing their points when given one? Find out using these three Open Middle problem from Bryan Anderson.
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
www.openmiddle.com/creating...
Where else do you get to see a real-life example of "long-run" probability play out in 32 seconds? This poker-based lesson will help students discover the difference between theoretical and experimental probability.
robertkaplinsky.com/work/vi...
robertkaplinsky.com/work/vi...
December 24, 2025 at 11:14 PM
Where else do you get to see a real-life example of "long-run" probability play out in 32 seconds? This poker-based lesson will help students discover the difference between theoretical and experimental probability.
robertkaplinsky.com/work/vi...
robertkaplinsky.com/work/vi...
Are your high school students working with complex numbers? Try these two Open Middle problems out to see what misconceptions they have:
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
December 22, 2025 at 11:33 PM
Are your high school students working with complex numbers? Try these two Open Middle problems out to see what misconceptions they have:
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
www.openmiddle.com/complex-...
Check out my Depth of Knowledge matrix for elementary math and download a PDF version to print or share with others.
robertkaplinsky.com/depth-k...
robertkaplinsky.com/depth-k...
December 22, 2025 at 5:03 PM
Check out my Depth of Knowledge matrix for elementary math and download a PDF version to print or share with others.
robertkaplinsky.com/depth-k...
robertkaplinsky.com/depth-k...
Knowing when to take medicine two or three times a day is easy. It's much more challenging when it's five times a day! This lesson seems deceptively easy at first, but it's more challenging than students expect and really gets them thinking.
robertkaplinsky.com/work/me...
robertkaplinsky.com/work/me...
December 22, 2025 at 12:13 AM
Knowing when to take medicine two or three times a day is easy. It's much more challenging when it's five times a day! This lesson seems deceptively easy at first, but it's more challenging than students expect and really gets them thinking.
robertkaplinsky.com/work/me...
robertkaplinsky.com/work/me...
Have you ever shared information you were excited about yet you didn't get the reaction you expected? Perhaps it was because of how it was framed.
More here: robertkaplinsky.com/behavio...
More here: robertkaplinsky.com/behavio...
December 21, 2025 at 1:13 AM
Have you ever shared information you were excited about yet you didn't get the reaction you expected? Perhaps it was because of how it was framed.
More here: robertkaplinsky.com/behavio...
More here: robertkaplinsky.com/behavio...
I really enjoyed this breakdown of the most common types of data visualization from Datalabs Agency. Check out how they organize them here: www.datalabsagency.com/2024...
December 20, 2025 at 8:07 PM
I really enjoyed this breakdown of the most common types of data visualization from Datalabs Agency. Check out how they organize them here: www.datalabsagency.com/2024...