Correct Answer: A

Rationale: To add fractions, find a common denominator, which in this case is 40. Convert each fraction to have the common denominator: 7/8 = 35/40, 9/10 = 36/40, and 6/5 = 48/40. Add these fractions to get 119/40. Simplify this improper fraction to a mixed number, which is 3 & 39/40. Choice B and C are incorrect as they do not represent the sum of the fractions. Choice D is incorrect; the whole number part should be 3, not 2.

Correct Answer: A

Rationale: To calculate the dose for a 2-year-old child using Fred's rule, we substitute the child's age (24 months) and the adult dose (15 mg) into the formula: (24 x 15) / 150 = 2.4 mg. Therefore, the correct answer is A, representing 2.4 mg for a 2-year-old child. Choice B is incorrect as it does not match the calculated dose. Choice C is incorrect as it does not consider the formula provided. Choice D is incorrect as it does not reflect the correct calculation based on the given information.

Correct Answer: B

Rationale: To solve the proportion 0.1:10=x:400, first, simplify the left side to 1:100. Then, set up the proportion as 1:100=x:400. Cross multiply to get x = 4. Therefore, the correct answer is B. Choice A (5) is incorrect because it does not match the calculated value of x. Choice C (50) is incorrect as it is not the result of solving the proportion provided. Choice D (25) is incorrect as it does not align with the correct calculation of x.

Correct Answer: C

Rationale: To add mixed numbers, first add the whole numbers together, then add the fractions. 6 + 8 = 14. For the fractions: 3/4 + 1/6 = (18 + 4) / 24 = 22/24 = 11/12. Therefore, 6 & 3/4 + 8 & 1/6 equals 14 & 11/12. Choice A is incorrect as it does not represent the correct sum. Choice B is incorrect because it does not match the correct result. Choice D is incorrect as it simplifies to 12 & 1/6, not 12 & 3/24.

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.