Khan Academy and Multiplying and Dividing with Scientific Notation

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SWBAT to multiply and divide with numbers in scientific notation

Big Idea

Students need as many opportunities to practice and reflect as we can give them.

Assessment Overview

10 minutes

This assessment can be done at home or in class. Either way, I ask students to prepare for the assignment by watching the video I created to help students. 


This activity can be incredibly helpful if students slow down and take the time needed to think about what they are doing and why it makes sense. 

Khan Academy is constantly changing its layout and its scoring system, but for this activity I would ask students to log in (optional) and work until they achieve mastery. This is a topic you need to discuss with students. "Mastery" in Khan Academy might mean something like getting 20 correct, but I want students to complete about 10 questions and only continue if they think they need more practice.

Teacher Note: I have had many students complain about Khan Academy. They get frustrated, because if they make a single mistake they need to basically start from the beginning. Most students find this discouraging. If they work and work even after they understood the topic, they sometimes spend a lot of time trying to achieve "mastery" and the project gets derailed if they hit the wrong key on the keyboard. In order to overcome this, I encourage my students to stop and reflect: "Do I need more practice?" 

The Assessment

40 minutes

There are currently 5 scientific notation exercise sets on Khan Academy. This assessment might be best to do before the orders of magnitude activity (even though Khan lists the exercises in the reverse order). I like this activity because it give students a chance to master a fundamental topic. 

The structure of the site is overwhelming to many students. To simplify the process, I have them log in to Khan Academy and then open a second tab and go straight to this link:

Mult. and Div. Scientific Notation

They could also go to the exercise dashboard and type in "multiplying and dividing scientific notation."

Exercise Dashboard


Last year I set this up in a series of assignments through my website: 

Shaun Teaches

This exercise is new and was not used last year, but I will use it in future assessment lessons.

The key is to ask students a follow up question. The guidelines are as follows:

1. Finish the Multiplying and Dividing Scientific Notation Exercise Until you reach "mastery"

2. As you work, write the questions and answers in your notebook

3. When you are finished, annotate your notes and explain some general observations you made as you worked. 

4. Create solve and explain a challenge problem that would fit in this exercise group. 

5. Answer this question and use examples to support your reasoning: What is the product of (3 x 10^2) and (6 x 10^5) in scientific notation? What is the quotient of these numbers (try both orders)? Explain how you know you are right.

I usually ask for the parts 4 and 5 via email. Since all students have set me up as a coach I can easily monitor their progress after class. I circulate during class and help students by asking them reflective questions, like "when you move the decimal, what are you doing to the number?"

I collect the notes from at least one student who has mastered the topic and one who is struggling with recent topics.

Assessment Review

10 minutes

I finish this assessment by reviewing questions with the class. I log into Khan Academy and project for the whole class to see. I popcorn around the room and ask students to solve and explain. For each question I get at least 2 algorithms, since students love to hear other strategies. I have noticed that many students use one strategy throughout all the problems and are usually so tired of it by the end that they crave a more efficient strategy. I wait until the end to share all strategies because I believe that process of struggling helps them process the importance of a more efficient strategy. If we just shared at the start, I think many students would blindly plug in the more efficient strategy without understanding why or how it is efficient.