Chalk Talk part 2 #makthinkvis

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Another task I presented students in the form of a Chalk Talk

We had previously used a patty paper lesson to construct our kites. image

Simply enough, we constructed the kite by first creating an obtuse angle, with different side lengths. Folding along AC, tracing original obtuse angle using a straightedge to form the kite. Immediately students made comments about the line of symmetry. They were given time to investigate side lengths, angles, diagonals, etc. forming ideas and testing them to prove properties.

Their Chalk Talk task was to devise a plan to calculate the area of a kite.

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Most every group approached the problem by dissecting the kite into right triangles, then combining areas. Several approached dissection as top triangle/bottom triangle, but would have to adjust their thinking when I asked them test their idea with specific total diagonal lengths. Some even extended the kite to create a rectangle. In the end, our discussion centered around 3 statements/procedures for finding area of a kite.

1/2(d1*d2) (d1*d2)/2 d1*d2

Allow them to determine which will /will not work and share evidence as to their conclusions. (Hello! MP3 critique reasoning of others.)

Sure, it would have been quicker to say here’s the formula, here’s a worksheet, practice, learn it. But its so much more fun “listening” to their Chalk Talk. Again, the end discussion is key-allowing them to think / work through each group’s findings, address any misconceptions and finally coming to a concensus as a class.

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4 responses »

  1. Not only MP3, but also MP1, 2, 6, 7, and 8.

    Thanks for sharing your students’ work and for allowing them to discover the formula. The time spent will benefit them much more in the long run than filling the same time with practice of a formula you give to them and they crunch out some low-level thinking to plug in numbers in the area formula…even if you dress it up and try to make it a “real world” problem about building a kite.

  2. I like that idea, Pam. Chalk talk to solve a specific problem. Very cool. The thing about getting them to figure out the formula themselves is that they now have ownership of that formula, it is not something just out of the book, and they have learnt strategies for figuring out other things in the future. That is, they have worked as mathematicians, not users of algorithms.

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