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Copyright © 2013 by Mosby, an imprint of Elsevier Inc. All rights reserved. Math Tutor Answer Key

PART ONE: BASIC mAs AND TIME CONVERSIONS

Working with Decimal TimersExercise 1: Calculating Total mAs Values 1. 5 mAs 2. 6.4 mAs 3. 1.9 mAs 4. 12.5 mAs 5. 80 mAs 6. 4 mAs 7. 10 mAs 8. 12.8 mAs 9. 30 mAs 10. 3 mAs 11. 25 mAs 12. 60 mAs 13. 80 mAs 14. 1.6 mAs 15. 0.6 mAs 16. 7 mAs 17. 9 mAs 18. 21 mAs 19. 210 mAs 20. 30 mAs 21. 150 mAs 22. 480 mAs 23. 3.6 mAs 24. 4.8 mAs 25. 30 mAs 26. 90 mAs 27. 12 mAs 28. 4.5 mAs 29. 75 mAs 30. 7.5 mAs 31. 45 mAs 32. 1.8 mAs 33. 1.2 mAs 34. 4 mAs 35. 16 mAs 36. 28 mAs 37. 64 mAs 38. 6.4 mAs 39. 132 mAs 40. 320 mAs 41. 280 mAs 42. 2.8 mAs 43. 40 mAs 44. 15 mAs 45. 100 mAs 46. 350 mAs 47. 3.5 mAs 48. 62.5 mAs

Working with Fractional TimersExercise 2: The 100 mA Station 1. 50 mAs 2. 5 mAs 3. 2 mAs 4. 20 mAs 5. Approximately 12 mAs 6. Approximately 1.2 mAs 7. Approximately 8 mAs 8. Approximately 0.8 mAs 9. Approximately 15 mAs 10. Approximately 7 mAs 11. 2.5 mAs 12. Approximately 33 mAs 13. Approximately 3.3 mAs 14. Approximately 16 or 17 mAs 15. Approximately 1.6 or 1.7 mAs 16. Approximately 66 or 67 mAs

Exercise 3: The 200 mA and 50 mA Stations 1. Approximately 24 or 25 mAs 2. 2.5 mAs 3. 40 mAs 4. 4 mAs 5. Approximately 6 mAs 6. Approximately 2.4 or 2.5 mAs 7. Approximately 16 or 17 mAs 8. Approximately 1.6 or 1.7 mAs 9. Approximately 4 mAs 10. Approximately 0.4 mAs 11. Approximately 7 to 8 mAs 12. Approximately 14 mAs 13. 5 mAs 14. Approximately 16 or 17 mAs 15. Approximately 1.6 or 1.7 mAs 16. Approximately 66 or 67 mAs 17. Approximately 6.6 or 6.7 mAs 18. Approximately 32 to 34 mAs 19. Approximately 3.2 to 3.4 mAs 20. Approximately 132 to 134 mAs 21. Approximately 8 to 9 mAs 22. Approximately 0.8 to 0.9 mAs 23. Approximately 0.6 to 0.7 mAs 24. Approximately 30 mAs

Exercise 4: The 300 mA Station 1. 60 mAs 2. 50 mAs 3. 6 mAs 4. 5 mAs 5. 15 mAs

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Math Tutor Answer Key Copyright © 2013 by Mosby, an imprint of Elsevier Inc. All rights reserved.

6. 150 mAs 7. 20 mAs 8. 25 mAs 9. 2.5 mAs 10. 12 mAs 11. 75 mAs 12. 7.5 mAs 13. Approximately 36 mAs 14. Approximately 3.6 mAs 15. Approximately 45 mAs 16. 20 mAs

Exercise 5: The 400, 500, and 600 mA Stations 1. 20 mAs (4 sets of 5) 2. 25 mAs (5 sets of 5) 3. 30 mAs (6 sets of 5) 4. 80 mAs (4 sets of 20) 5. 120 mAs (6 sets of 20) 6. 8 mAs (4 sets of 2) 7. 12 mAs (6 sets of 2) 8. 125 mAs (5 sets of 25) 9. 150 mAs (6 sets of 25) 10. 12.5 mAs (5 sets of 2.5) 11. 15 mAs (6 sets of 2.5) 12. 20 mAs (1⁄3 of 60, or 6 sets of 3.3) 13. Approximately 13 mAs (4 sets of 3.3) 14. Approximately 6.4 mAs (4 sets of 1.6) 15. Approximately 60 mAs (4 sets of 15) 16. 100 mAs (4 sets of 25) 17. Approximately 4.8 to 5 mAs (4 sets of 1.25) 18. Approximately 60 mAs (5 sets of 12) 19. Approximately 48 to 50 mAs (6 sets of 8) 20. Approximately 5 mAs (6 sets of .8) 21. Approximately 40 mAs (5 sets of 8) 22. Approximately 3.2 to 3.3 mAs (4 sets of 0.8) 23. Approximately 28 mAs (4 sets of 7) 24. Approximately 35 mAs (5 sets of 7) 25. Approximately 16 mAs (4 sets of 4) 26. Approximately 20 mAs (5 sets of 4) 27. Approximately 24 mAs (6 sets of 4) 28. Approximately 120 to 132 mAs (4 sets of 33)

Exercise 6: Complex Fractions 1. 40 mAs 2. Approximately 14 mAs (2 sets of 7) 3. Approximately 21 mAs 4. 15 mAs (3 sets of 5) 5. 35 mAs 6. 150 mAs 7. 80 mAs (2 sets of 40) 8. 120 mAs 9. 160 mAs 10. 60 mAs 11. 140 mAs 12. Approximately 28 to 30 mAs (2 7 2) 13. Approximately 42 mAs (2 7 3) 14. 30 mAs (3 sets of 10) 15. 70 mAs 16. 160 mAs (2 sets of 80) 17. 240 mAs

18. 320 mAs 19. 120 mAs (3 × 40) 20. 280 mAs 21. 200 mAs 22. 120 mAs (2 × 60) 23. 180 mAs 24. 240 mAs 25. 90 mAs 26. 210 mAs (7 × 30) 27. 40 mAs (2 × 20) 28. 60 mAs 29. 45 mAs (3 × 15) 30. 60 mAs 31. 140 mAs 32. 200 mAs 33. 150 mAs 34. 700 mAs ([7/5] × 500) 35. 75 mAs (3 × 25) 36. 240 mAs (2 × 120) 37. 360 mAs 38. 180 mAs (3 × 60) 39. 90 mAs (3 × 30) 40. 120 mAs*

(*Note that on question 40 you may simply take double the answer you would get at the 300 mA station. If you have memorized that 15 s and 20 s go together at the 300 mA station, then a fifteenth at 600 would be double 20 or 40. Then take 3 sets of 40. Many problems at the 600 mA station can be solved this way—by just doubling the answer you would get at 300 mA. Also, many mAs values can be figured at the 400 mA station in a similar manner by doubling numbers you are familiar with using at the 200 mA station.)

Timers: Converting Fractions into Decimals and Vice VersaExercise 7: Converting Fractions Into Decimals 1. 0.75 2. 0.667 3. 0.25 4. 0.2 5. 0.167 6. 0.142 7. 0.125 8. 0.083 9. 0.0667 10. 0.05 11. 0.04 12. 0.033 13. 0.025 14. 0.02 15. 0.0167 16. 0.0125 17. 0.01 18. 0.005 19. 0.7 20. 0.133 21. 0.15 22. 0.4 23. 0.6

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24. 0.8 25. 0.33 26. 0.2 27. 0.35 28. 0.0067 29. 0.375 30. 0.3125

Exercise 8: Converting Decimals Into Fractions 1. 1⁄20

2. 1⁄30 (common denominator is 333) 3. 1⁄5 4. 3⁄4 5. 1⁄40

6. 2⁄3 7. 1⁄7 (common denominator is 143) 8. 1⁄500

9. 4⁄50

10. 1⁄6 (common denominator is 167) 11. 1⁄8 12. 3⁄5 13. 1⁄16

14. 1⁄120 (common denominator is 833)

FINDING mA AND TIME COMBINATIONS FOR A DESIRED mAsExercise 9: Warm-up Calculations 1. 2 sets of 40 2. 3 sets of 15 3. 2 sets of 33 4. 3 sets of 25 5. 3 sets of 60 6. 3 sets of 40 or 2 sets of 60 7. 2 sets of 80 or 4 sets of 40 8. 3 sets of 80 or 4 sets of 60 9. 3 sets of 30 10. 4 sets of 80

Exercise 10: Calculations Using Fractions 1. 1⁄25

2. 1⁄40

3. 2⁄3 (2 sets of 33) 4. 1⁄15

5. 1⁄6 6. 1⁄12

7. 1⁄30

8. 1⁄60

9. 1⁄80

10. 1⁄120

11. 2⁄5 (2 sets of 20) 12. 1⁄30

13. 1⁄20

14. 1⁄2 15. 1⁄8 16. 1⁄5 17. 3⁄5 (3 sets of 40) 18. 1⁄40

19. 1⁄40

20. 2⁄15 (2 sets of 7)

21. 1⁄6 22. 1⁄50

23. 1⁄15

24. 1⁄120

25. 3⁄20 (3 sets of 15) 26. 3⁄5 (3 sets of 60) 27. 4⁄5 (4 sets of 60) 28. 1⁄4 (cut in half twice) 29. 1⁄5 30. 3⁄5 (3 sets of 80)

Exercise 11: Calculations Using Decimals 1. 0.04 2. 0.025 3. 0.67 4. 0.07 5. 0.16 6. 0.08 7. 0.033 8. 0.017 9. 0.4 10. 0.05 11. 0.025 12. 0.125 13. 0.2 14. 0.6 15. 0.025 16. 0.0125 17. 0.07 18. 0.17 19. 0.02 20. 0.07 21. 0.6 22. 0.25 23. 0.2 24. 0.6

Technique AdjustmentsExercise 12: Applying the 15% Rule for kVp, Applying the Rule in Steps, Applying the Rule in Portions 1. 6 2. 4.5 3. 4 4. 2.5 5. 3 6. 10.5 7. 6 8. 9 9. 16.5 10. 3 11. Approximately 5 12. 6 13. Approximately 4 14. Approximately 7 15. 9 16. 102 kVp 17. 46 kVp 18. 64 to 65 kVp 19. 74 kVp

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Math Tutor Answer Key Copyright © 2013 by Mosby, an imprint of Elsevier Inc. All rights reserved.

PART TWO: MATHEMATICS OF RADIOGRAPHIC TECHNIQUES

Exercise 13: Adjusting for Distance Changes, the Inverse Square Law, the Square Law: Rules of Thumb for Distance Changes 1. Approximately 75 2. Approximately 30 3. Approximately 30 4. Approximately 36 5. 15 6. 10 7. 15 8. 25 9. 68 to 70 10. Four times 11. Two times 12. 1⁄4

13. 1⁄2 14. 62.5 15. 3.47 16. 0.77 17. 0.28 18. 70 19. 12 in 20. 30 in 21. 40 in 22. 60 in 23. 1.17 24. 4.34 25. 8.1 26. 0.31 27. 0.69 28. 1.93 29. 0.56