'16-'17 General Discussion for Lesson 1.2

CS Principles Unit and Lesson Discussion
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Use this thread to discuss your questions and comments about how to run the lesson.

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I am confused by the answer to the question in Sending Numbers. The questions is “how many bits would you need to send numbers for a 96 x 96 chart?” Which to me means, “how many bits to represent the number 96?” Which would be 7. The possible answers are 10, 13, 14 and 16 and the correct answer is 14. Wouldn’t a better answer be 2 sets of 7 bits? One 14 bit number wouldn’t work.

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I am wondering what materials students used most for this activity - any suggestions from people who have already done it?

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@jranta I thought of this as if I had a 96x96 chart, and numbered each square I would have ~9200 squares. If I were to assign each square a number I would only need to count to 9216. Since a 14 bit number holds ~16000 numbers (values) I could assign each of the 9216 squares a 14 bit number. But I am curious about your “2 sets of 7 bits” - what makes that a better answer?

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My thinking is that this is more efficient if it’s thought of as an x, y (96 x 96) grid. Columns are x (numbered 1 to 96) and rows are y (numbered 1 to 96). Thus you’d need two numbers (7 bit bytes) to get to any point on the grid. I didn’t think of your system, where each square is assigned 1 number from 1 to 9216. Many students might approach it the way I did, so maybe reword the answers to include both answers somehow?

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Hi @jranta and @kaitie_o_bryan

Students could use either method for encoding the grid and should arrive at the same answer. It seems like you already talked through the number each grid answer. For using x and y coordinates you can think of the 14 bits number as actually representing two numbers as once or a (x,y) coordinate pair. Often for computers a one number is sent and a protocol is used to break apart the different components. So in essence its two 7 bit numbers but grouped together as one number. So for example

Here is a 14 bit number: 00101010101010

Here is the protocol for decoding it:

Hope that helps

-Dani

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String is always popular. Colored construction paper was popular this year. Last year it was flashlights, maybe because we were in the basement cafeteria when we did it where it was darker. Creative random stuff leads to creative random solutions. One team liked the Google Sunglasses I had leftover from some event.

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SO… my second time teaching this whole unit, I realized that there feels like there are a lot of “steps” to each lesson as a teacher - it can feel overwhelming. HOWEVER, the second time, I realized that every lesson has the same flow: there’s a problem you give students, they try to solve it, and they formalize their solution in a protocol, you discuss the protocol and the connection to the “real world”. Once I realized that, I felt like this unit seemed much more cohesive and approachable as a teacher. Hopefully that’s helpful for newer teachers to the course!

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Questions like, “Which do you prefer Pizza or Tacos” were less effective then questions like, “Do you like the Patriots?”

My students tended toward concrete devices such as a pipe cleaner slice of pizza and a pipe cleaner taco. I think I will use Yes / No questions as examples next time.

I think the instructions are a bit confusing. Next time I will will be more clear that I what they are doing is sending ANSWERS not the questions.

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The risk of yes / no questions is that you can’t expand them when you need to move to questions with 4, 8, 16…possible answers. It’s not a huge deal, they just have to think up a new question.

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I plan on teaching this lesson soon and was wondering about the sending complex messages device activity. I assume the the students will keep changing their question to come up with 4,8, and N possible messages.

But does the type of question matter here anymore?

First they start with a binary question but then I guess they will change the binary question to a ‘non-binary’ question so that they can come up with 8 possible answers. Thoughts?

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@irimina

I have taught this lesson where I asked the students to adjust their question to fit the number of answers in the challenge and all groups moved together from challenge to challenge. Last week, I allowed groups to move to the next challenge when they are ready and I just ask them to adjust their device to have more possible answers. When the group presented, I had them demonstrate enough ‘answers’ to understand how their device works.

Happy computing,
Andrea