The least common multiple (LCM) of two numbers is the smallest number that is a multiple of both. Which of the following represents the LCM of 14 and 21?

Correct Answer: C

Rationale: Rationale: To find the least common multiple (LCM) of 14 and 21, we need to determine the smallest number that is a multiple of both 14 and 21. First, list the multiples of 14: 14, 28, 42, 56, 70, 84, ... Next, list the multiples of 21: 21, 42, 63, 84, ... The smallest number that appears in both lists is 42. Therefore, the LCM of 14 and 21 is 42.

Correct Answer: B

Rationale: 1/4 gram is equivalent to 1/4 * 1000 milligrams (since 1 gram = 1000 milligrams). 1/4 * 1000 = 250 milligrams. Therefore, the equivalent dosage in milligrams is 250mg, which corresponds to option B. The other choices are incorrect because they do not correctly convert 1/4 gram to milligrams using the conversion factor of 1 gram = 1000 milligrams.

Correct Answer: A

Rationale: To add 12 1/21 and 3 1/3, first add the whole numbers: 12 + 3 = 15. Then, add the fractions: 1/21 + 1/3. To find a common denominator, multiply 21 by 3 to get 63. Convert 1/21 to an equivalent fraction with a denominator of 63 by multiplying the numerator and denominator by 3, resulting in 3/63. Now add 3/63 (equivalent to 1/21) and 21/63 (equivalent to 1/3) to get 24/63. Simplifying 24/63 gives 8/21. Therefore, the sum is 15 8/21. Choices B, C, and D are incorrect because they do not result from the correct addition of the given numbers and fractions.

Correct Answer: A

Rationale: To convert a decimal to a percent, move the decimal point two places to the right. Therefore, 0.0068 as a percentage is 0.68%. Choice A is correct because it represents the correct conversion. Choice B is incorrect as it would be the decimal 6.8 represented as a percentage. Choice C is incorrect as it would be the decimal 0.068 represented as a percentage. Choice D is incorrect as it is the original decimal value.

Correct Answer: C

Rationale: To solve the proportion 9:14 = x:56, you can cross multiply to get 9 * 56 = 14 * x. This simplifies to 504 = 14x. Dividing by 14 on both sides gives x = 36. Therefore, the value of x in the proportion is 36. Choice A, x = 14, is incorrect as it does not satisfy the proportion equation. Choice B, x = 25, is incorrect as it is not the value that makes the proportion true. Choice D, x = 42, is incorrect as it does not correctly satisfy the proportion equation.

Correct Answer: B

Rationale: To administer 20 mg of the medication, you would need 25 mL. This calculation is derived from the concentration of 4 mg per 5 mL. By setting up a proportion, you can determine that for 20 mg, 25 mL must be administered as follows: (20 mg / 4 mg) = (x mL / 5 mL). Solving for x results in x = 25 mL. Choice A is incorrect because it miscalculates the proportion. Choices C and D are incorrect as they do not account for the correct concentration of the medication.

Correct Answer: A

Rationale: To find the total area covered by the stones, multiply the number of stones by the area each stone covers: 1,200 stones * 0.75 sq ft = 900 sq ft. Therefore, the stones will cover 900 sq ft, which is closest to 800 sq ft among the answer choices A, B, C, and D. The correct answer is A, 800 sq ft. Choices B, C, and D are incorrect as they do not result from the correct calculation of multiplying the number of stones by the area each stone covers.

Correct Answer: D

Rationale: To find the value of x, cross multiply in the ratio 18:x=10:300. This gives 18 * 300 = 10 * x. Solving for x, x = 540. Therefore, the correct answer is D. Choice A (16), Choice B (180), and Choice C (30) are incorrect because they do not satisfy the proportion equation 18:x=10:300 when cross multiplied.

Correct Answer: A

Rationale: If 3 bags of chips cost $4.50, then the cost per bag is $4.50/3 = $1.50. To buy five bags, John would need to pay 5 bags * $1.50 = $7.50. Therefore, it will cost John $7.50 to buy five bags of chips. The other choices are incorrect because they do not accurately calculate the total cost based on the given information.