42 Chapter 1Solving Linear Equations 39. MODELING WITH MATHEMATICS One type of stone formation found in Carlsbad Caverns in New Mexico is called a column. This cylindrical stone formation connects to the ceiling and the  oor of a cave.columnstalagmite a. Rewrite the formula for the circumference of a circle, so that you can easily calculate the radius of a column given its circumference. b. What is the radius (to the nearest tenth of a foot) of a column that has a circumference of 7 feet? 8 feet? 9 feet? c. Explain how you can  nd the area of a cross section of a column when you know its circumference. 40. HOW DO YOU SEE IT? The rectangular prism shown has bases with equal side lengths.bb a. Use the  gure to write a formula for the surface area S of the rectangular prism. b. Your teacher asks you to rewrite the formula by solving for one of the side lengths, b orℓ. Which side length would you choose? Explain your reasoning.41. MAKING AN ARGUMENT Your friend claims that Thermometer A displays a greater temperature than Thermometer B. Is your friend correct? Explain your reasoning.ygygyg100201030405060708090100FThermometer AThermometer B42. THOUGHT PROVOKING Give a possible value for h. Justify your answer. Draw and label the gure using your chosen value of h.A 40 cm28 cmhMATHEMATICAL CONNECTIONS In Exercises 43 and 44, write a formula for the area of the regular polygon. Solve the formula for the height h.43. bhcenter 44. bhcenterREASONING In Exercises 45 and 46, solve the literal equation for a.45. x a + b + c
— ab 46. y x ( ab — a b ) Maintaining Mathematical ProficiencyMaintaining Mathematical ProficiencyEvaluate the expression. (Skills Review Handbook) 47. 15 5 + 52 48. 18 ⋅ 2 42 8 49. 33 + 12 3 ⋅ 5 50. 25(5 6) + 9 3Solve the equation. Graph the solutions, if possible. (Section 1.4) 51. x 3 + 4 9 52. 3y 12 7 2 53. 2 2r + 4 16 54. 4 s + 9 24Reviewing what you learned in previous grades and lessons