Correct Answer: B

Rationale: To determine how much money Karen has left, we first calculate the total cost of the items she bought: $1.85 + $3.20 + $3.05 = $8.10. Subtracting this total cost from the initial amount she had, $40 - $8.10 = $31.90 left. Choice A, $30.95, is incorrect as it does not reflect the correct amount left after subtracting the total cost. Choice C, $32.10, is incorrect as it is the total cost of the items she bought, not the amount left. Choice D, $34.95, is incorrect as it does not consider the expenses incurred and subtracted from the initial amount.

Correct Answer: D

Rationale: 1 milliliter (mL) is equal to 1000 micrograms (mcg). Therefore, to find out how many milliliters are needed for 250 micrograms: 250 mcg · 1000 = 0.25 mL. So, the healthcare professional should draw up 0.25 milliliters of the drug to administer 250 micrograms subcutaneously. Choice A, 0.00025 milliliters, is incorrect as it is too small a volume for the required dosage. Choice B, 0.0025 milliliters, is also too small. Choice C, 0.025 milliliters, is 100 times greater than the correct answer of 0.25 milliliters. Therefore, the correct answer is 0.25 milliliters.

Correct Answer: B

Rationale: To find 6.4% of 32, first calculate 6.4% as a decimal (0.064) and then multiply it by 32 to get 2.048. When rounding to the tenths place, 2.048 is rounded to 2.1 because the digit after the tenths place is 8, which is equal to or greater than 5. Choice A is incorrect as it does not reflect the accurate calculation. Choices C and D are also incorrect because they do not match the correct result of multiplying 6.4% by 32 and rounding to the tenths place.

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.

Correct Answer: B

Rationale: To convert 17/80 to a percent, we divide 17 by 80 to get 0.2125. Multiplying by 100, we get 21.25%. Rounding to the nearest whole number, 21.25% becomes 21%. Choice A (20%) is incorrect because rounding 21.25% down to the nearest whole number gives 21%. Choice C (22%) is incorrect as it is the next whole number after 21. Choice D (23%) is incorrect as it is more than 21.25% and thus rounds up to 22%.