-numbered exercises. O Finding a Sum In Exercises 55-60, find the partial sum. 9.2 Arithmetic Sequences and Partial Sums 627 72. Brick Pattern A triangular brick wall is made by cutting some bricks in half to use in the first column of every other row (see figure). The wall has 28 rows. The top row is one-half brick wide and the bottom row is 14 bricks wide, How many bricks are in the finished wall? nce 55) Σ 100 56. , 7n 500 n=51 5λ Σ (1 +8) 250 58. (1000 – n) 100 59. 2(-6n + 20) 75 60. (12n – 9) Matching an Arithmetic Sequence with Its Graph In Exercises 61-64, match the arithmetic sequence with its graph. [The graphs are labeled (a)–(d).] ametic Sequence • • 73. Falling Object (a) an (b) an An object with negligible air resistance is dropped from the top of the E five terms of the 24 8. rely. 18 12 Willis Tower in Chicago at a height of 1451 feet. During 2 4 6 8 the first second of 2 4 6 8 10 9- -2 fall, the object falls 16 feet; during the -4+ (c) second second, it falls 48 feet; during the third second, it falls 80 feet; during the fourth second, it falls 112 feet. Assuming this pattern continues, how many feet does the object fall in the first 7 seconds after it is dropped? an (d) an 30 10 mula In Exercises ns of the arithmetic the missing term. 24 8. 18- 12 74. Prize Money A county fair is holding a b goods competition in which the top eight bakers re- cash prizes. First place receives $200, second receives $175, third place receives $150, and so c 2 4 68 10 2 4 68 10 -2 62. а, 3 Зл — 5 64. a, = 25 – 3n (a) Write the nth term (a) of a sequence that repr the cash prize received in terms of the place baked good is awarded. 61. a, = -in + 8 63. a, = 2 + in 3 %3D 3 A Graphing the Terms of a Sequence In Exercises 65-68, use a graphing utility to graph the first 10 terms of the sequence. (Assume that n begins with 1.) %3D (b) Find the total amount of prize money awa the competition. hmetic Sequence the sum of the finite 75. Total Sales An entrepreneur sells $15,00 of sports memorabilia during one year and se of increasing annual sales by $5000 each yea next 9 years. Assuming that the entrepreneur r goal, find the total sales during the first 10 yes business. What kinds of economic factors cou 66. a, = -5 + 2n = -0.3n + 8 = -5+ 65. an 3. 15 - 2n 68. an 67. a, = 0.2n + 3 + 16 + 18 + 20 %3D 9. Job Offer In Exercises 69 and 70, consider a job 76. Borrowing Money You borrow $5000 parents to purchase a used car. The arrang the loan are such that you make paymen onth toward the balance plus 1% inte Dotermine the total compensation from Ucars of employment. the business from meeting its goals? a)with the given starting salary and annual raise. (a) Determine the salary during the sixth year of m the previous month. nayme 6 4+ 2.