Math Quiz tomorrow on dividing decimals

Dear Families,

Tomorrow we are having a quiz on dividing decimals using long division. We practiced this skill all last week in math review and today students took a practice quiz, then we went over the answers. Between their math reviews last week (in their math notebook) and the practice quiz, they should have lots to review to get ready for tomorrow's quiz. But just in case anyone wants more to practice, here is a link to some extra practice problems and their answers. There is no need to have these checked in with me in the morning.

• Level 2 practice [link]
  
• Level 3 practice: [link]
  
• Level 4 practice: [link]
  

How I've Taught the Skill:

We've looked at this as an extension of long division. Most students had done long division in 5th grade, but for a few their first time learning it was earlier this year in our math reviews. I believe the same process we've practiced in class is demonstrated in these videos:

• http://www.youtube.com/watch?v=HlEx1TN-dqY
  
• http://www.youtube.com/watch?v=2PU5JshO0xA
  

Why does it work?

Well, this algorithm is the same one we all learned in school. And at first it seems like it's just a magic trick. But really, this is based in the equivalent fractions that students learned earlier in the year. I tried to help students understand this reasoning, but really, most of them needed to focus on practicing the steps so I believe only a few cared about 

1. 1/2 and 5/10 are equivalent fractions... to get to 5/10 from 1/2 you just multiply the numerator and the denominator by 5. But they both have a decimal value of 0.5... so they are equivalent. 
2. Let's say I want to divide 4.5 by 0.9. I can write that division in fraction format as 4.5/0.9. If I multiply the top and the bottom by 10, it becomes 45/9. The decimal seems to have moved one spot to the right for each one. 
3. That's the same thing that we are doing in decimal division. By moving the divisor's decimal one place to the right, we are multiplying it by 10. If we have to move it two spaces to the right, we are multiplying it by 100. We do the same thing to the divisor so that it is equivalent to the original math problem and it will have the same answer.

This Quiz Counts for Spring Semester

I will record this math quiz in the Spring semester so that students can have the opportunity to revise their work and improve.

Thank you,

Brian MacNevin