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Concept explainers
. Exponential growth and decay laws. Consider the following cases of exponential growth and decay.
- Create an exponential function of the form \[Q = {Q_0} \times {(1 + r)^t}\] (where r >0 for growth and r <0 for decay) to model the situation described. Be sure to clearly identify both variables in your function.
- Create a table showing the value of the quantity Q for the first 10 units of time (either years, months, weeks, or hours) of growth or decay.
c. Make a graph of the exponential function.
29. A privately owned forest that had 1 million acres of old growth is being clear cut at a rate of 7% per year.
30. A town with a population of 10,000 loses residents at a rate of 0.3% per month because of a poor economy. 31. The average price of a home in a town was $175,000 in 2013, but some prices are rising by 5% per year.
32. A certain drug breaks down in the human body at a rate of 15% per hour. The initial amount of the drug in the bloodstream is 8 milligrams. 33. Your starting salary at a new Job is $2000 per month, and you get annual raises of 5% per year. 34. You hid 100,000 rubles in a mattress at the end of 1991, when they had a value of $10,000. However, the value of the ruble against the dollar then fell 50% per year.
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Chapter 9 Solutions
Using & Understanding Mathematics: A Quantitative Reasoning Approach (7th Edition)
- An editor wants to analyze if there is a significant difference in the ratings of books in four different genres. Random samples of book ratings were collected for four different genres. The editor recorded ratings in a 0 to 10 scale in the following table. Fiction Novel Biography Science&Technology 8.5 8.4 6.2 9.1 5.3 5.3 5.5 4.3 7.7 4.2 7.0 9.7 5.1 9.8 9.3 5.2 6.9 8.6 6.7 7.9 4.8 7.1 6.9 8.4 Shall we reject or not reject the claim that there are no differences among the population means of book ratings for the different genres? Use.arrow_forwardThe same final exam of the astronomy course was given to two groups of students. The maximum number of points that a student can score is 100. The first group consisted of a random sample of 10 students who were taught by Professor A. Students from the first group obtained the following results: 87 88 91 88 86 92 81 93 73 99 The second group consisted of a random sample of 9 students who were taught by Professor B. Students from the second group obtained the following results: 74 74 79 97 67 88 86 83 78 Compute the mean squares of between-group variability, MSBET. Round your answer to two decimal places.arrow_forwardQ3 3 Points 1 0 2 4 0 6 01 5 - -1 0 10 00 0 0 1 1 The reduced row echelon form of the augmented matrix of a linear system is given above. Describe the solution set of this linear system in parametric vector form. Please select file(s) Select file(s) Save Answerarrow_forward
- 3. Suppose you have 12 professors in a department and you have to chose members of departmental committees. (a) How many ways can you pick members for one 4 people committee? (b) How many ways can you pick members for two different 4 people committees if no-one can serve on both committees? (c) How many ways can you pick members for two different 4 people committees if people can serve on both committees? (d) How about if you need members for a 4 person, a 5 person, and a 3 person committee, people cannot serve on more than one committee? (e) How about if you need members for a 4 person, a 5 person, and a 3 person committee, people can serve on more than one committee? (f) How about if you need members for a 4 person, a 5 person, and a 3 person committee, people cannot serve on more than one committee, and the first person chosen for each committee serves as chair?arrow_forwardPeggy conducted a study to identify the randomness of rainy days in fall. For 15 days, she recorded whether it rained that day or not. They denoted a rainy day with the letter R, a day without rain with the letter N. R N N R R N N R R N N R R R R Test the sequence for randomness. Use .arrow_forwardConsider the grades for the math and history exams for 10 students on a scale from 0 to 12 in the following table. Student Math History 1 4 8 2 5 9 3 7 9 4 12 10 5 10 8 6 8 5 7 9 6 8 9 6 9 11 9 10 7 10 Compute the Spearman correlation coefficient. Round your answer to three decimal places.arrow_forward
- Q4 3 Points 1 Let A = 2 3 7 5 11 Give one nontrivial solution X of the homogeneous system Ax = 0. (Your vector x should have explicit numbers as its entries, as opposed to variables/parameters). Show your work for how you found it. Please select file(s) Select file(s) Save Answerarrow_forwardTo compare two elementary schools regarding teaching of reading skills, 12 sets of identical twins were used. In each case, one child was selected at random and sent to school A, and his or her twin was sent to school B. Near the end of fifth grade, an achievement test was given to each child. The results follow: Twin Pair 1 2 3 4 5 6 School A 169 157 115 99 119 113 School B 123 157 112 99 121 122 Twin Pair 7 8 9 10 11 12 School A 120 121 124 145 138 117 School B 153 90 124 140 142 102 Suppose a sign test for matched pairs with a 1% level of significance is used to test the hypothesis that the schools have the same effectiveness in teaching reading skills against the alternate hypothesis that the schools have different levels of effectiveness in teaching reading skills. Let p denote portion of positive signs when the scores of school B are subtracted from the corresponding scores of school…arrow_forwardA horse trainer teaches horses to jump by using two methods of instruction. Horses being taught by method A have a lead horse that accompanies each jump. Horses being taught by method B have no lead horse. The table shows the number of training sessions required before each horse performed the jumps properly. Method A 25 23 39 29 37 20 Method B 41 21 46 42 24 44 Method A 45 35 27 31 34 49 Method B 26 43 47 32 40 Use a rank-sum test with a5% level of significance to test the claim that there is no difference between the training sessions distributions. If the value of the sample test statistic R, the rank-sum, is 150, calculate the P-value. Round your answer to four decimal places.arrow_forward
- A data processing company has a training program for new salespeople. After completing the training program, each trainee is ranked by his or her instructor. After a year of sales, the same class of trainees is again ranked by a company supervisor according to net value of the contracts they have acquired for the company. The results for a random sample of 11 salespeople trained in the last year follow, where x is rank in training class and y is rank in sales after 1 year. Lower ranks mean higher standing in class and higher net sales. Person 1 2 3 4 5 6 x rank 8 11 2 4 5 3 y rank 7 10 1 3 2 4 Person 7 8 9 10 11 x rank 7 9 10 1 6 y rank 8 11 9 6 5 Using a 1% level of significance, test the claim that the relation between x and y is monotone (either increasing or decreasing). Verify that the Spearman rank correlation coefficient . This implies that the P-value lies between 0.002 and 0.01. State…arrow_forwardSand and clay studies were conducted at a site in California. Twelve consecutive depths, each about 15 cm deep, were studied and the following percentages of sand in the soil were recorded. 34.4 27.1 30.8 28.0 32.2 27.6 32.8 25.2 31.4 33.5 24.7 28.4 Converting this sequence of numbers to a sequence of symbols A and B, where A indicates a value above the median and B denotes a value below the median gives ABABABABAABB. Test the sequence for randomness about the median with a 5% level of significance. Verify that the number of runs is 10. What is the upper critical value c2? arrow_forwardSand and clay studies were conducted at a site in California. Twelve consecutive depths, each about 15 cm deep, were studied and the following percentages of sand in the soil were recorded. 34.4 27.1 30.8 28.0 32.2 27.6 32.8 25.2 31.4 33.5 24.7 28.4 Converting this sequence of numbers to a sequence of symbols A and B, where A indicates a value above the median and B denotes a value below the median gives ABABABABAABB. Test the sequence for randomness about the median with a 5% level of significance. Verify that the number of runs is 10. What is the upper critical value c2?arrow_forward
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