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# Lesson 9: Proportion and Scale

Lesson Component Description of Component For This Lesson
Lesson Opening   (10 minutes)     Introduction of New Material (15 - 20 minutes)   Objective: To use proportionality to find missing lengths of similar figures and determine values based on scale. SWBAT: (1) Create the correct proportion given similar figures or a map scale (2) Solve proportions for the unknown length.   I will use a “Do Now” to simple fractions. Students will be allowed to use calculators. Which is greater? a. or b. or   (2) Mini-lesson I will place on the blackboard two maps and explain the scale markings. I will give an example of a 1”:1 mile scale and ask how far a student would have to walk to cover 3.5” on the map. (2) Engagement For other examples of proportion I will use:

 Statue of Liberty Pedestal to the tip of the torch: 151 ft 1 in Right arm: 42 ft. Length of the hand: 16 ft 5 in. Length of the index finger: 8 ft.

 Sterling silver is an alloy Its composition is 37/40 silver and 3/40 copper. What is the ratio of silver to copper?

Student Practice of New Material   (35-40 minutes)   (10) Exploration/Application Proportions are equations of two ratios. We use the cross-product of these ratios to solve for the unknown in a proportion. Examples of ratios: How many students are in this classroom? How many male students and female students are in this classroom? What is the ratio of the number of female students to that of male students? What is the ratio of the number of male students to the total number of students? What is the student to teacher ratio? What is the typical student teacher ratio?   Different ways to express ratio   a to b a:b a/b there are a for every b.       (4) Assessment The assessment will be ongoing as I walk around the room observing students.   Individual Exercise   Impact p. 521 Problem Set A. For #2, Simply the ratio   Group Work   p. 524 Share and Summarize
Summary (5 minutes) I will restate the idea of a proportion as an equation of two ratios.   Exit Ticket “Which map would cover more area, one with a scale of 1” to 100 miles or one with a scale of 1” to 250 miles? On which map would you be able to see more detail? Explain.

Date: 2015-12-24; view: 269

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