8/17/15: Happy Right Triangle Day!

It’s 8/17/15, or as I like to think of it, Right Triangle Day!

8-15-17 Triangle

Since

8^2 + 15^2 = 17^2

we know that 8, 15, and 17 are the lengths of the sides of a right triangle.  Informally, we say this is true because of the Pythagorean Theorem, but technically it’s true because of the converse of the Pythagorean Theorem.

It’s been a while since we’ve celebrated a Right Triangle day, and it won’t be long before we get to celebrate another.  To commemorate this numerical novelty, the Museum of Mathematics is teaming up with the Pacific Science Center to pythagorize Seattle’s Triangle Pub.  They certainly had fun pythagorizing the Flatiron building in NYC on 5/12/13!

Enjoy being right today!

Regents Recap — June 2015: Pointless Questions

Here is another installment in my series reviewing the NY State Regents exams in mathematics.

I really do not understand the point of questions like this, from the June 2015 Geometry Regents exam.

2015 GEO 12Why do we manufacture artificial multiple choice questions to assess whether or not students understands geometric constructions?  Why not just ask them to construct something?

Moreover, the construction aspect of this question is essentially irrelevant:  the question might as well be, “Which diagram shows an altitude?”.

The Regents exam writers have been using this approach in testing geometric constructions for some time.  It just seems pointless to me.  And it is often the case that the exam also includes a free-response question that asks the student to actually construct something with a compass, which makes this multiple choice question both pointless and redundant.

Much is made about the importance of testing when it comes to student learning and teacher accountability.  But such arguments seem less reasonable the more closely we look at what we test and how we test it.

Regents Recap — June 2015: Common Core Geometry Structure

Here is another installment in my series reviewing the NY State Regents exams in mathematics.

June, 2015 saw the administration of the first Common Core Geometry Regents exam in New York.  This exam will replace the Geometry Regents exam, which was also offered this testing cycle.

The CC Geometry exam has fewer multiple choice questions (24) than the Geometry exam (28).  It is worth noting that this change, in and of itself, likely will reduce average scores, as random guessing on those four extra questions would, on average, earn 2 points.  The free response sections are structured slightly differently, but not substantially so.  These differences mirror those between the new Common Core Algebra exam, introduced last year, and the old Integrated Algebra exam (see here).

The two Geometry exams are not drastically different, though there is greater emphasis on transformations on the CC Geometry exam, which I covered here.   However, there are some minor differences that have impact.

First, the multiple choice questions on the CC Geometry exam definitely seem a bit harder, on average, than those on the old Geometry exam.  One place this is apparent is the higher frequency of questions that ask the student to identify the false statement, rather than the true statement.  Here are two questions similar in content, one from each exam:  Question 20 from the CC exam (top) and Question 16 (bottom) from the non-CC exam.

2015 CC GEO 20

2015 GEO 16Generally speaking, I’d say it’s more challenging to identify a statement that is not always true than one which must be true.  There are three such problems on the CC exam, compared with one on the old exam.

Question 26 on the CC exam exemplifies the increased emphasis on explaining one’s work.

2015 CC GEO 26

A more traditional question might simply ask for the measure of angle NLO.  Here, the measure of the angle is given, and the student is asked to provide the mathematical justification for that value.

Lastly, our teacher team was somewhat surprised at how closely the exam tracked the sample items that were released by the state.  For example, the segment partitioning problem on the CC Geometry exam

2015 CC GEO 27

was very similar to a sample item

CC Sample Segment partitionAdditionally, the construction problem on the CC Geometry exam

2015 CC GEO 25was identical to problem 12 in the Fall sample items.

Our Geometry teacher team generally found this inaugural CC Geometry exam to be in line with our expectations in terms of content and difficulty.  If anything, we were surprised at how unsurprising it was to us.

More the anything related to the Common Core exam, the level of difficulty of the old Geometry exam given during the same cycle surprised us.  The multiple choice section seemed to be more challenging than those of past recent exams, which made us wonder if the two exams drew their multiple choice questions from a single pool.

Regents Recap — June 2015: Common Core Geometry and Transformations

Here is another installment in my series reviewing the NY State Regents exams in mathematics.

June, 2015, saw the administration of the first Common Core Geometry Regents exam in New York.  I led a teacher team that worked to adapt our curriculum to the Common Core standards.  One of our primary concerns was how the new transformation-based approach to Geometry inherent in the Common Core standards would be represented on this Regents exam.  In particular, we had no idea how establishing congruence and similarity via transformations, an apparent emphasis of the standards, would be assessed.

A total of 18 of the 86 points on the exam (around 21%) were associated with transformations:  six multiple choice questions and two free response questions.  Here are a few examples, with associated Common Core standards in parentheses.

Question 10 is about rotations that map regular polygons onto themselves (CCSS.MATH.CONTENT.HSG.CO.A.3).

2015 CC GEO 10

Question 16 assesses the concept that dilation can alter length but must preserve angle measure (CCSS.MATH.CONTENT.HSG.SRT.B.5).

2015 CC GEO 16

Question 24 addresses establishing congruence by rigid motions (CCSS.MATH.CONTENT.HSG.CO.B.7).

2015 CC GEO 24

Question 30 asks the student to explicitly connect transformations to congruence by recalling the fundamental principles that underlie rigid motions (CCSS.MATH.CONTENT.HSG.CO.B.6).

2015 CC GEO 30

And Question 33 asks to student to first produce a “traditional” proof of congruence, and then interpret the congruence through a rigid motion (CCSS.MATH.CONTENT.HSG.CO.C.11).  This is a simple way to connect the two concepts.

2015 CC GEO 33

Overall, the manner in which transformations were tested aligned with our expectations, both in scope and in content.  Our Geometry worked closely together throughout the year, integrating a variety of resources from New York state and elsewhere, but mostly felt in the dark about what the test would look like.  In the end, we were pleasantly surprised.  But we also noticed how much different the Common Core Algebra exam was in year two, so we know that we may be surprised again.

Math Photo: Hexagonal Rabbits

Hexagonal Rabbits

The tilling station is one of my favorite exhibits at the Museum of Mathematics.  These rabbit tiles create a hexagonal tiling of the plane.  Pick any rabbit, and you’ll notice six rabbits all around it; this is exactly how hexagons fit together to tile the plane.

What I really like about this tiling is the the various levels of triangles that emerge.  Triangles of rabbits, one of each color, mutually intersect at ears and paws.  And I can’t help but seeing the monochromatic rabbit triangles!

 

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