Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Section 3.5 – Write Ratios and Proportions Ratio – uses division to compare to quantities where Ratios can be written in 3 ways a to b Proportion – is an equation that states that two ratios are equivalent. a : b Each Ratio is read as “ the ratio of a to b", then Cross Product Property – the cross product of a proportion are equal. Cross Product – is the product of the numerator of one ratio and the denominator of the other ratio, in a proportion. If Extremes of the proportion are a and d. Means of the proportion are b and c. The Cross Product Property is also called the Means-Extremes Property.

Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Example # 1 At a carwash fundraiser, 18 ninth grade students and 14 tenth grade students worked the shift Find the ratio of ninth grade students to tenth grade students. Section 3.5 – Write Ratios and Proportions a) oror 9 to 7 Find the ratio of ninth grade students to all students. b) oror 9 to 16

Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Example # 2 Solve the proportion : Write original proportion. Simplify Check your Solution. Divide each side by 12. Cross Product Property Simplify Section 3.6 – Solve Proportions Using Cross Products a) Write original proportion. Simplify Check your Solution. Divide each side by 6. Cross Product Property Distribute and Simplify b) Subtract 3x from each side Simplify

Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Georgia is making her own potting soil. For every 4 buckets of peat moss, she mixes in 3 buckets of perlite. Suppose she uses 10 buckets of peat moss. How many buckets of perlite should she use? Write and solve a proportion to find the answer. Georgia should use 7.5 buckets of perlite in her mixture with peat moss. Example # 3 Section 3.6 – Solve Proportions Using Cross Products Write a proportion involving two ratios that compare the amount of peat moss with the amount of perlite. Write original proportion. Simplify Check your Solution. Divide each side by 4. Cross Product Property Simplify

Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Section 3.6 – Solve Proportions Using Cross Products Scale Model – a three-dimensional model of an object in which the dimensions of the model are in proportion to the dimensions of the object. Scale Drawing – a two-dimensional drawing of an object in which the dimensions of the drawing are in proportion to the dimensions of the object. Scale – relates the drawing’s or model’s dimensions and the actual dimensions in a ratio.

Chapter 3 – Solving Linear Equations Algebra I A - Meeting 16 Homework # 12 pg 165 # 21 – 30 all pg 171 # 16 – 30 even Scale Drawing of a Room of a House (Don’t forget to have a Scale) Section