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7.1 Ratios. Purpose: To solve problems using ratios. Homework: p. 289 1-31 odd and p. 291 (problems) 1-9 all. Express the ratio pf 3 to 8 in 3 different ways. 3 ÷ 8 3 : 8 3 8. Write each ratio in simplest form. 45x:30x = 3/2 18ab² 14a²b = 9b 7a. Expressing Ratios.
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7.1 Ratios • Purpose: To solve problems using ratios. • Homework: p. 289 1-31 odd and p. 291 (problems) 1-9 all.
Express the ratio pf 3 to 8 in 3 different ways. 3 ÷ 8 3 : 8 3 8 Write each ratio in simplest form. 45x:30x = 3/2 18ab² 14a²b = 9b 7a Expressing Ratios
5 days : 18 hours You need the same unit of measure for both. 1 day = 24 hours so 5 days = 120 hours. 120 hours 18 hours = 20:3 or 20/3 Write the ratio of the weight of a 20g marble to a 30kg bowling ball. Convert to the same unit. 1000kg = 1g. 20g = 20g 30kg 30,000g = 1:1500 Expressing Ratios (cont.)
Solving Ratios • The ratio of boys to girls enrolled in chemistry is 5:4. If the total number of students taking chemistry is 981, how many boys and girls are enrolled in chemistry? • Let 5x = # of boys and 4x = # of girls. • Add 5x + 4x = 981 and Solve for x. • 9x = 981, x = 109 • You now need to plug 109 into the x’s so • 5(109) = 545 boys 4(109) = 436 girls
Solving Ratios (cont.) • The heights of 3 brothers are in the ratio13:14:15. Their combined heights equal 210 in. Find the height of each brother. • Let the heights = 13x, 14x 15x. • Add 13x + 14x + 15x = 210. SOLVE. • 42x = 210. x = 210. PLUG IN. • 13(210), 14(210), 15(210) • The heights are 65 in., 70 in., and 75 in.