Correct Answer: A

Rationale: To express the ratio 25:80 as a percentage, follow these steps: First, divide 25 by 80: 25/80 = 0.3125. Then, multiply by 100 to convert to a percentage: 0.3125 100 = 31.25%. Therefore, the ratio 25:80 is equivalent to 31.25%. Choice A is correct. Choice B (34%) is incorrect because it does not accurately represent the ratio 25:80. Choice C (41.25%) and Choice D (43.75%) are also incorrect as they do not match the calculated percentage for the given ratio.

Correct Answer: C

Rationale: To express 2/5 as a decimal, you divide the numerator (2) by the denominator (5). 2 · 5 = 0.4. Choice A (0.2) is the decimal equivalent of 1/5, not 2/5. Choice B (0.25) is the decimal equivalent of 1/4, not 2/5. Choice D (2.5) is not the correct decimal equivalent of 2/5 as it is greater than 1.

Correct Answer: B

Rationale: To multiply 5.04 by 2, you simply multiply the two numbers together: 5.04 x 2 = 10.08. Therefore, the correct answer is B. Choice A (1.008) is incorrect as it represents the result of dividing 5.04 by 5 instead of multiplying. Choice C (10.8) is incorrect as it is the result of rounding 10.08 to the nearest whole number. Choice D (18) is incorrect as it results from adding 5.04 and 2 instead of multiplying.

Correct Answer: B

Rationale: To calculate how much Donald earns from selling a house for $152,000 at an 8% commission rate, we multiply the selling price by the commission rate: $152,000 x 0.08 = $12,160. Therefore, he earns $12,160. Choice A, $12,160, is the correct answer as calculated. Choices C and D are incorrect amounts as they do not result from the given information. Choice C, $19,000, is significantly higher than the correct calculation, and choice D, $21,600, is the result of incorrectly adding the commission to the selling price instead of calculating the commission earned.

Correct Answer: B

Rationale: To find the final concentration, first, calculate the total volume of the solution (2 ml + 8 ml = 10 ml). Then, determine the concentration by dividing the volume of the concentrated medication by the total volume and multiplying by 100%: (2 ml / 10 ml) * 100% = 20%. Therefore, the correct answer is B. Choice A (16.67%) is incorrect as it does not represent the correct calculation. Choices C (25%) and D (50%) are both incorrect as they do not reflect the accurate concentration resulting from the dilution process.