Correct Answer: A

Rationale: The correct answer is A: 3000 meters. To convert kilometers to meters, you need to know that there are 1000 meters in 1 kilometer. Therefore, to find the number of meters in 3 kilometers, you multiply 3 by 1000, resulting in 3000 meters. Choice B, 2000 meters, is incorrect as it doesn't account for the correct conversion factor. Choice C, 3500 meters, and Choice D, 2500 meters, are also incorrect as they provide inaccurate conversions.

Correct Answer: C

Rationale: Calculate the increase in dosage: 100mg * 20% = 100mg * 0.20 = 20mg. Add the increase to the original dosage to find the new dosage: 100mg + 20mg = 120mg. Therefore, the new dosage is 120mg after a 20% increase from the original 100mg dosage. Choice A (80mg) is incorrect because it represents a decrease rather than an increase. Choice B (100mg) is the original dosage and does not account for the 20% increase. Choice D (140mg) is incorrect as it is the original dosage plus 40%, not the 20% increase specified.

Correct Answer: D

Rationale: When a die is rolled, there are 3 odd numbers (1, 3, 5) out of a total of 6 possible outcomes. The probability of rolling an odd number is calculated by dividing the number of favorable outcomes (3) by the total number of outcomes (6), resulting in a probability of 3/6 or 50%. Therefore, the correct answer is D. Choices A, B, and C are incorrect because they do not reflect the correct probability calculation for rolling an odd number on a standard six-sided die.

Correct Answer: B

Rationale: The correct answer is B. To find the result of multiplying 10 by 5, you perform the calculation: 10 5 = 50. Choices A, C, and D are incorrect because they do not represent the accurate product of 10 multiplied by 5.

Correct Answer: B

Rationale: In the metric system, there are 1000 grams in 1 kilogram. To convert kilograms to grams, you multiply the number of kilograms by 1000. Therefore, 4 kilograms would equal 4000 grams. Choice A (400 grams) is incorrect because it is the result of multiplying by 100, not 1000. Choice C (40 grams) is incorrect as it is the result of dividing by 1000 instead of multiplying. Choice D (100 grams) is incorrect as it is a random figure and not the correct conversion from kilograms to grams.