SETTING UP AND SOLVING RATIOS AND PROPORTIONS Ratio

SETTING UP AND SOLVING RATIOS AND PROPORTIONS

• Ratio – Comparison of 2 numbers by division. – Example: 1: 2, ½, 1 to 2 • Proportion – An equation stating that 2 ratios are equal. – Example: a: b = c: d

Example Which of the following pairs of ratios do not form a proportion? Which ones do? Cross Multiply Not a proportion

Set up and solve this proportion. 8) 5 is to 4 as 45 is to x. ss o cr ly w ip o N ult m 5 = ____ 45 ____ 4 x 5 x = 180 5 5 x = 36

First - Set up & solve the proportion. 9) 3 is to 2 as x is to 18. ss o cr ly w ip o N ult m 3 = ____ x ____ 2 18 2 x = 54 2 2 x = 27

NO set up this time!! Just solve…. . 10) 6 x = 144 6 6 x = 24

11) 16 m = 8 16 16 m = Now Reduce

12) Mr. Jones has taken a survey of college students and found that 40 out of 47 students are liberal arts majors. If a college has 10, 827 students, what is the number of students who are liberal arts majors, rounded to the nearest whole number? First – Set up Your proportion! ss o cr ly w ip o N ult m x 40 = _______ 47 10, 827 47 x = 433, 080 47 47 x = 9214

13) Geothermal energy is heat from inside the earth. Underground temperatures generally increase 9°C for every 300 meters of depth. How deep would a well have to be for the temperature to reach 216°C ? First – Set up Your proportion! 9° = _____ 216° ____ 300 m 9 m = 64800 9 9 m = 7200

14) A map has a scale of 1 cm = 30 km. If two cities are 11 cm apart on the map, what is the actual distance between the two cities to the nearest tenth of a km? First – Set up Your proportion! 11 cm = _____ 30 km x 1 x = 330 km