Lesson plan

Determine a cube's edge length when given the surface area by using division and algebraic reasoning

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teaches Common Core State Standards 6.EE.A.2.c http://corestandards.org/Math/Content/6/EE/A/2/c
teaches Common Core State Standards 6.G.A.4 http://corestandards.org/Math/Content/6/G/A/4
teaches Common Core State Standards MP2 http://corestandards.org/Math/Practice/MP2
teaches Common Core State Standards MP6 http://corestandards.org/Math/Practice/MP6
teaches Common Core State Standards MP7 http://corestandards.org/Math/Practice/MP7
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Big Ideas: Given the surface area of a cube, its edge length can be determined using algebraic reasoning with the formula S.A. = 6s^2. Formulas for finding volume use variables for which measurements can be substituted. This lesson builds on students' work finding the surface area of cubes using the formula S.A. = 6s^2. This task requires students to use division and algebraic reasoning to find the edge lengths of various cubes when given the surface area. Students explore how to rewrite S.A. = 6s^2 as S.A. / 6 = s^2; they will use their understanding of square numbers (whole-number factors, not exceeding 12 x 12) to find the side length. This lesson develops algebraic reasoning, introduces the need for finding square roots, and connects to finding surface area of more complex figures in 7th grade. Vocabulary: 2-dimensional shape, 3-dimensional figure, area, cube, cubic units, edge, edge length, exponent, formula, side, side length, square units, surface area, volume