Correct Answer: C

Rationale: The metric system is based on powers of 10, making calculations and conversions easier because each unit increases or decreases by a factor of 10. This factor allows for a simple and consistent way to move between different units within the system. Choice A, 'The length of Napoleon's forearm' is incorrect as the metric system is not based on a physical attribute but on a standardized mathematical factor. Choice B, '2,' and Choice D, 'Atomic weight of helium,' are also incorrect as they do not align with the foundational principle of the metric system being based on powers of 10.

Correct Answer: D

Rationale: To find the total number of chapters, divide the total number of pages by the number of pages per chapter: 798 · 6 = 133 chapters. If he reads 2 chapters a day, it will take him 133 · 2 = 66.5 days to finish the book. Therefore, the correct answer is 66.5 days. Choice A is incorrect because it miscalculates the number of days required. Choices B and C are incorrect as they do not consider the correct calculation based on the given information.

Correct Answer: A

Rationale: To solve the proportion 120:x::40:0.5, cross-multiply to get 120 * 0.5 = 40 * x. This simplifies to 60 = 40x. Dividing both sides by 40 gives x = 1.5. Therefore, the correct answer is A. Choice B (60) is incorrect because x is not equal to 60. Choice C (0.167) is incorrect as it does not result from solving the proportion. Choice D (16) is also incorrect because x is not equal to 16.

Correct Answer: C

Rationale: Rationale: - The imaginary unit, denoted as "i," is defined as the square root of -1. - Therefore, 5i can be expressed as 5 times the square root of -1, which is equivalent to 5√-1. - Option A, -5, is a real number and not an imaginary unit multiple. - Option B, i^5, is equal to i because i raised to any power that is a multiple of 4 results in 1, and i^5 is equivalent to i. - Option D, 1/5i, is the reciprocal of 5i and not equivalent to 5i.

Correct Answer: A

Rationale: The probability of getting a '1' on a six-sided die is 1 out of 6 possible outcomes, making it a 1/6 probability. Therefore, choice A is correct. Choices B, C, and D are incorrect because they do not represent the correct probability of rolling a '1' on a standard six-sided die.