# 4. Compare ratios using unit rate: What's the best deal? (C)

teaches Common Core State Standards CCSS.Math.Content.6.RP.A.2 http://corestandards.org/Math/Content/6/RP/A/2
teaches Common Core State Standards CCSS.Math.Content.6.RP.A.3b http://corestandards.org/Math/Content/6/RP/A/3/b
teaches Common Core State Standards CCSS.Math.Practice.MP2 http://corestandards.org/Math/Practice/MP2

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Lesson objective: Understand that every ratio can be written as a unit rate.

Students bring prior knowledge of using ratios to solve problems from 6.RP.3. This prior knowledge is extended to use unit rates to compare ratios that are not easily scaled up or down. A conceptual challenge students may encounter is understanding that the ratio bar is also a division sign.

The concept is developed through work with ratio tables and division, which helps students see that there are multiple ways to compare ratios.

This work helps students deepen their understanding of equivalence because any ratio can be written as a unit rate.

Students engage in Mathematical Practice 2 (Reason abstractly and quantiatively) as they create appropriate representations (ratio tables or division sentences) and consider the units involved in finding the unit rate.

Key vocabulary:

• ratio table
• division bar
• proportional relationship

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