Reflection: Connection to Prior Knowledge The Cup Half Full (day 1 of 3) - Section 2: Warm up


I had to change the warm up question on the fly. The original question read "If I buy 20 cupcakes the bakery will give me 10% more for free! Will that be enough for the class?" As I was circulating during the warm up I noticed students having trouble starting with the right ratio. They were writing 10/20 & 20/100 as well as the correct 10/100. When I asked them to explain how they got that or what those numbers represented they couldn't make sense of them. The ones that did have the correct 10/100 could only explain that the 10 represented the percent, but couldn't tell me what the actual numbers 10 & 100 represented. Students are not accustomed to using the context to make sense of the numbers and were simply trying to do something with the numbers, which students will do when they are used to blindly following an algorithm.

I decided to change the first question so that they could make sense of what the 10 and the 100 represented. Instead I asked "If I buy 100 cupcakes, the bakery will give me 10 for free. What percent is that?" Once they were able to make sense of the percent as a ratio that counted and compared the number of cupcakes for free and the number of cupcakes bought most of them were able to set it up correctly.

I already knew we were entering treacherous waters when we started working with percent because of the wide range of prior knowledge gaps with fraction and place value sense. Even though I didn't predict this particular difficulty it didn't catch me totally off guard because I expected to have to make adjustments along the way during this lesson. It is important to meet the kids at their level. They will have trouble making sense of new information if they are busy trying to make sense of something else.

  Connection to Prior Knowledge: Scaffolding on the fly
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The Cup Half Full (day 1 of 3)

Unit 8: Exploring Rational Numbers
Lesson 12 of 20

Objective: SWBAT determine 10% of any number mentally.

Big Idea: When the decimal "moves" to the left the digits are actually moving to the left because their value is 10 times less.

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4 teachers like this lesson
Math, Number Sense and Operations, prior knowledge, percent of a number, Mental Math, fraction sense, decimal sense, Flexibility, rational numbers
  54 minutes
the cup half full
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