Correct Answer: C

Rationale: To find the volume of a cone, we use the formula: (1/3) * π * (radius)^2 * height. Substituting the given values: (1/3) * π * (5cm)^2 * 12cm = 150 cu cm. Therefore, the correct answer is C. Choice A, B, and D are incorrect as they do not correspond to the correct calculation using the formula for the volume of a cone.

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: The correct answer is C: 5,000 grams. There are 1,000 grams in a kilogram. Therefore, to convert kilograms to grams, you need to multiply the number of kilograms by 1,000. In this case, 5 kilograms is equal to 5 1,000 = 5,000 grams. Choices A and D are incorrect as they incorrectly multiply by 10,000 instead of 1,000. Choice B is incorrect as it divides instead of multiplies, leading to an incorrect conversion.

Correct Answer: B

Rationale: To convert grams to milligrams, you need to multiply by 1,000 because there are 1,000 milligrams in 1 gram. Therefore, to find out how many milligrams are in 3.4 grams, you multiply 3.4 by 1,000 which equals 3,400 mg. Choices A, C, and D are incorrect because they do not correctly convert grams to milligrams.

Correct Answer: A

Rationale: When adding two negative numbers, you add their absolute values and keep the negative sign. In this case, -5 + (-8) is equal to -13 because the absolute values of 5 and 8 add up to 13, and the negative sign is retained. Choice B (8) is incorrect because adding two negative numbers results in a negative sum. Choice C (13) is incorrect as it doesn't consider the negative signs of the numbers being added. Choice D (-5) is incorrect because it does not account for the addition of the two negative numbers.