1. Purpose: To Solve problems using proportions. Homework: p. 295 1-35 odd, and p. 296 1-9 all.

2. Notes Two equal ratios are called proprtions. 2:3 = 4:6 or 2 = 4 » 3 6 12 = 12 In the proportion a:b = c:d, a and d are the extremes and b and c are the means. CROSS PRODUCTS ARE EQUAL!!!

3. Examples x = 5 3 12 Cross products are equal. 12x = 15 x = 15/ 12 or 5/4 or 1.25 3x + 1 = x 5 2 Cross products are equal. 2(3x +1) = 5x Solve for x. 6x + 2 = 5x -5x -2 x = {-2}

4. Examples (cont.) x – 5 = x + 2 12 5 Cross Products. 5(x – 5) = 12(x + 2) Solve. 5x – 25 = 12x + 24 7x = -49 x = {-7} 4x + 12 = x + 3 8 2 Cross products. 8x + 24 = 8x + 24 Identity. You will not have NS until lesson 4.

5. Word Problems An investment of $1200 paid interest of $ 102. How much interest would $1600 invested at the same rate for the same amount of time pay? Set up a proportion. 1200 = 1600 ****Units of measure need 102 x to be the same on top. Solve for x. 102(1600) = 1200x 19200/1200 = 136 or $136

6. Word Problems (cont.) A typist types an essay of 1260 words in 15 min. At that rate, how long would it take to type an essay of 2100 words? Set up your proportion. 1260 = 2100 (words) 15 x (time in min.) 1260x = 15(2100) x = 25; 25 min.