4. The table shows the U.S. population and the number of Americans over age 65 at 10-year intervals since 1940 (about when the Social Security program was created). mnmmmmmm U.S. Americans average 12.7 17.2 26.1 31.9 a) What is the percentage increase in the US. population between 1940 and 2010? b) What is the percentage increase in the over-65 population between 1940 and 2010? c) In 2010, there were approximately 165 million Americans of working age (25-65). Estimate (Assume L o_fthis population is working), the number of people who were actually working and contributing to Social Security in 2010. Compare this number to the over-65 population. d} How do these results affect the future of programs such as Social Security and Medicare? PART 2 - Growth: Linear versus Exponential Lab 5. Based on information in Deep River Jim's Wilderness Trail Book, the rate at which crickets chirp varies linearly with the temperature. At 59 F., they make 76 chirps per minute, and at 65 F., they make 100 chirps per minute. a) Is this a linear or exponential function? b} Predict the chirping rate for 70 F. and 100 F. c) What would you predict the temperature to be if you counted 150 chirps per minute? 6. In 2014, the enrollment at a certain university was 3000 student. Enrollment has been increasing by 2% per year. a) Is this a linear or exponential function? b} Predict what the enrollment will be in the year 2018. c) When will the enrollment reach approximately 3250? 7. The number of dollars it costs you a month to own a car depends on the number of kilometers you drive it that month. Based on figures in Changing Times Magazine, it costs about $153 a month if you drive 300 kilometers, and $230 a month if you drive 1500 kilometers. Assume that a linear function is a reasonable mathematical model of the way cost varies with distance. a) Is this a linear or exponential function? bl Predict your monthly cost if you drive 500, 1000, and 2000 kilometers per month. c) About how far could you drive in a month without exceeding a cost of $250