Lesson 17.2 Understanding Percents

This lesson falls near the beginning of a cluster of lessons that deals with proportional reasoning concepts, including ratio, rate, proportion, and percent. This lesson stresses visuals, familiar contexts, and mental math to promote sense-making strategies to find percents of numbers. In earlier lessons, students linked percents to fractions and decimals. In future lessons, students learn routines for these computations.

Important features of the lesson: Visuals (SP6): students estimate the fullness of containers, relying on benchmark percents, such as 50%, 25%, and 10%. Familiar contexts (SP6-9): students find simple percents of a dollar and of a meter. Later, students use mental strategies to find more difficult percents of amounts, based on benchmarks. Multiple strategies are recommended and illustrated in the Math Background (TP10).

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