Correct Answer: A

Rationale: To solve X/4 = 9/x, cross multiply to get x^2 = 36. Taking the square root of both sides gives x = 6. Choice A is correct because x = 6 satisfies the equation x^2 = 36. Choices B, C, and D are incorrect as they do not satisfy the equation when substituted back into it.

Correct Answer: A

Rationale: To subtract 7 7/10 from 3 4/5, first convert 3 4/5 to have the same denominator as 7 7/10. Converting 4/5 to 8/10, the subtraction becomes 7 7/10 - 3 8/10. Subtracting, 7 - 3 = 4 and 7/10 - 8/10 = -1/10. Therefore, the result is 3 4/5 - 7 7/10 = 3 9/10. Choices B, C, and D are incorrect because they do not reflect the correct subtraction of fractions and whole numbers in this scenario.

Correct Answer: A

Rationale: The correct answer is A, which is 30.48. To convert inches to feet, since there are 12 inches in a foot, you need to multiply the conversion factor from inches to centimeters (2.54 cm) by the number of inches in a foot (12). This gives 30.48 cm in 1 foot. Choice B, 35, is incorrect as it does not follow the correct conversion. Choices C and D, 25 and 40 respectively, are also incorrect conversions and do not align with the conversion factors provided in the question.

Correct Answer: B

Rationale: To divide 40.3 by 4.8, you perform the calculation: 40.3 · 4.8 ≈ 8.4. Therefore, the correct answer is 8.4. Choice A (7.5) is incorrect as it is the result of dividing 40.3 by 5.4. Choice C (6.2) is incorrect as it is the result of dividing 40.3 by 6.5. Choice D (9.1) is incorrect as it is the result of dividing 40.3 by 4.4.

Correct Answer: A

Rationale: To convert the blood glucose level from millimoles per liter (mmol/L) to milligrams per deciliter (mg/dL), we need to perform a double conversion. 1 millimole is equivalent to 180.15 milligrams, and 1 liter is equal to 10 deciliters. First, multiply the glucose level (5.5 mmol/L) by the conversion factor for millimoles to milligrams (180.15 mg/mmol), then divide by the conversion factor for liters to deciliters (10 dL/L): 5.5 mmol/L * 180.15 mg/mmol / 10 dL/L ≈ 55 mg/dL. Therefore, the equivalent blood glucose level in mg/dL is 55. Choice A is correct. Choice B is incorrect as it does not account for the conversion factors properly. Choices C and D are significantly off as they do not follow the correct conversion calculations.