plywood could emit 140 g per hr. (Source: A. Hines, Indoor Air Quality & Control.) eye irtation can A 10onm has 100 f of new plywood flooring, Find a linear equation F that com- putes the amount of formaldehyde, in micrograms, emitted in x hours. (D) The room contains 800 ft' of air and has no ventilation. Determine how long t would take for concentrations to reach 33 g/t.(Round to the nearest tenth.) 44. Classroom Ventilation According to the American Society of Heating. Refriger- ating and Air-Conditioning Engineers, Inc. (ASHRAE), a nonsmoking classroom should have a ventilation rate of 15 ft' per min for each person in the rOom. (a) Write an equation that models the total ventilation V (in cubic feet per hour) necessary for a classroom with x students. (b) A common unit of ventilation is air change per hour (ach). One ach is equivalent to exchanging all the air in a room every hour. If x students are in a classroom having volume 15,000 ft', determine how many air exchanges per hour (A) are necessary to keep the room properly ventilated. (C) Find the necessary number of ach (A) if the classroom has 40 students in it. (a) in areas like bars and lounges that allow smoking, the ventilation rate should be increased to 50 ft per min per person. Compared to classrooms, ventilation should be increased by what factor in heavy smoking areas? 45. College Enrollments The graph shows the projections in total enrollment at degree- granting institutions from fall 2014 to fall 2021. Enrollments at Degree-Granting Institutions 30 25 22.0 22.3 22.5 22:823:2. 23.6.23.9 24.1 15 001 '14 '15 '16 17 '18 '19 '20 '21 Year Source: U.S. Department of Education, National Center for Education Statistics. The following linear model provides the approximate enrollment, in millions, between the years 2014 and 2021, where x = 0 corresponds to 2014, x = 1 to 2015, and so on, and y is in millions of students. y = 0.3143x + 21.95 %3D 20 10 Enrollment (in millions) 1.3 Complex Numbers 105 (a) Use the model to determine projected enrollment for fall 2018. (b) Use the model to determine the year in which enrollment is projected to reach 24 million. (c) How do your answers to parts (a) and (b) compare to the corresponding values shown in the graph? (d) The actual enrollment in fall 2000 was 15.3 million. The model here is based on data from 2014 to 2021. If we were to use the model for 2000, what would the projected enrollment be? (e) Compare the actual value and the value based on the model in part (d). Discuss the pitfalls of using the model to predict enrollment for years preceding 2014. Baby Boom U.S. population during the years between 1946 and 1964, commonly known as the Baby Boom, can be modeled by the following linear equation. y = 2.8370x + 140.83 %3D ere y represents the population in millions as of July 1 of a given year, and represents number of years after 1946. Thus, x = 0 corresponds to 1946, x= 1 1017 ond so on (Source: U.S. Census Bureau.)