Spring 2020 17. Silas owns a lemonade stand. He has found that the cost of operating the stand is given by C(x) = 3x²2 - 36x +120, where C(x) is the cost in dollars and x is the number of cups of lemonade (in dozens) he sells on a given day. Find the minimum cost? 18. Based on the table below, what is the probability that a randomly selected person (a) is an 8th grader? (b) is a 7th grader and likes Math/Science best? (c) prefers history, given that the person is an 8th grader? (d) is a 7th grader given that the person prefers English? Grade 7th Grade 8th Grade Totals English 38 47 85 X 0 P(X) 0.25 8 x²-11x+24 Favorite Subject by Grade Math/Science 28 72 100 History 36 45 81 19. A survey of a group of 8th graders revealed that 21% had an Instagram account, but not Snapchat. 14% had a Snapchat account, but not Instagram. 8% did not have either of these accounts. If the student is selected at what is the probability the student has both an Instagram account and a Snapchat account? random 20. Find the expected value of x for the following: 1 0.47 0.19 2 (b) f(x) = 3 4 x+4 x²-16 Other 14 18 0.05 0.02 32 Totals 116 182 298 5 21. The population of a LaLa Land is currently experiencing exponential growth. The population, in thousands, can be modeled with the functions A(t) = 108e0.013t where t is the number of years since 1980 (a) How many people lived in LaLa Land in the year 2015? (round to nearest person) (b) During what year did/will the population reach 150 thousand people? 6 22. One hundred twenty people were surveyed as to whether they owned dogs or cats. Ninety-five said they owned a dog. Sixty-one said they owned a cat. Seventeen said they did not own a dog or a cat. How many people surveyed on a dog and a cat? 3. Find the domain for: (a) f(x) = - 0.01 0.01 Beau solves a problem to find the number of freshmen, sophomores, and juniors to be on a committee. ote a system of equations and solved the system. She found the general solution was , y, z) = (2t-4, 10-t, t) How many solutions are there to her problem? Tanner has recently discovered the importance of saving all his phone data on iCloud quite often. The bability his phone will crash and he will lose some data is given by the function P(x) = 65+410g (x + 2)