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
Lesson plan