43. Medicine Cesium-137 is a radioisotope used in radiology where levels are measured in millicuries (mci). Use the graph below. What is a reasonable estimate of the half-life of cesium-137?

Cesium-137 Decay

C Challenge

44. Credit Suppose you use a credit card to buy a new suit for $250. If you do not pay the entire balance after one month, you are charged 1.8% monthly interest on your account balance. Suppose you can make a $30 payment each month.

    1. What is your balance after your first monthly payment?
    2. How much interest are you charged on the remaining balance after your first payment?
    3. What is your balance just before you make your second payment?
    4. What is your balance after your second payment?
    5. How many months will it take for you to pay off the entire bill?
    6. How much interest will you have paid in all?
45. Open-Ended Write two exponential growth functions f(x) and g(x) such that f ( x ) < g ( x ) f open x close less than g open x close  for x < 3 x less than 3  and f ( x ) > g ( x ) f open x close greater than g open x close  for x > 3 . x greater than 3 .

Standardized Test Prep

GRIDDED RESPONSE

SAT/ACT

46. A new fitness center opens with 120 members. Every month the fitness center increases the number of members by 40 members. How many members will the fitness center have after being open for 3 months?

    

47. What is the slope of the line?
48. What is the simplified form of 8 0 ? 8 to the , question mark
49. What is the simplified form of 5 − 2 ? 5 super negative 2 end super , question mark
50. A manufacturing company is making metal sheets with a thickness of 5.4 × 10 − 2 5.4 times , 10 super negative 2 end super  mm. What is 5.4 × 10 − 2 5.4 times , 10 super negative 2 end super  written in standard form?

Mixed Review

See Lesson 7-6.

Graph each function.

51. y = 2 · 10 x y equals 2 middle dot , 10 to the x
52. f ( x ) = 100 · 0 . 9 x f open x close equals 100 middle dot 0 . , 9 to the x
53. g ( x ) =   1 10 · 2 x g open x close . equals , 1 tenth . middle dot , 2 to the x

See Lesson 3-4.

Solve each inequality.

54. 7 x + 2 < 16 7 x plus 2 less than 16
55. 3 4 t − 4 ≥ 5 3 fourths , t , minus 4 greater than or equal to 5
56. − 0.08 > 0.35 k − 0.15 negative , 0.08 , greater than , 0.35 , k minus , 0.15

Get Ready! To prepare for Lesson 8-1, do Exercises 57–61.

See Lesson 1-7.

Simplify each expression.

57. 6 t + 13 t 6 t plus 13 t
58. 7 k − 15 k 7 k minus 15 k
59. 2 b − 6 + 9 b 2 b minus 6 plus 9 b
60. 4 n 2 − 7 n 2 4 , n squared , minus 7 , n squared
61. 8 x 2 + x 2 8 , x squared , plus , x squared

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