a lab needs 200ml of a 5 salt solution they only have a 10 solution how much 10 solution and water should be mixed
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HESI A2

HESI A2 Math Portion

1. A lab needs 200ml of a 5% salt solution. They only have a 10% solution. How much 10% solution and water should be mixed?

Correct answer: B

Rationale: Rationale: 1. Let x be the volume of the 10% solution needed and y be the volume of water needed. 2. The total volume of the final solution is 200ml, so x + y = 200. 3. The concentration of the final solution is 5%, so the amount of salt in the final solution is 0.05 * 200 = 10g. 4. The amount of salt in the 10% solution is 0.1x, and the amount of salt in the water is 0, so the total amount of salt in the final solution is 0.1x. 5. Since the total amount of salt in the final solution is 10g, we have 0.1x = 10. 6. Solving for x, we get x = 100ml. 7. Substituting x =

2. A cake recipe calls for 2½ cups of flour. How many cups are needed to make 6 cakes?

Correct answer: D

Rationale: To make one cake, you need 2½ cups of flour. To make 6 cakes, you would need 6 times the amount of flour for one cake, which is 2½ x 6 = 15 cups. Therefore, the correct answer is 15 cups. Choices A, B, and C are incorrect as they do not correctly calculate the total amount of flour needed for 6 cakes.

3. If x = -2 and m = -3, evaluate: xm - 2m

Correct answer: A

Rationale: Substitute x = -2 and m = -3 into the expression: (-2) * (-3) - 2 * (-3) = 6 + 6 = 12. Therefore, the correct answer is 12. The mistake in the other choices lies in the calculation. Choice B, 6, is the result of adding the two terms instead of subtracting the second term from the first. Choice C, 8, and Choice D, 10, are also incorrect as they do not follow the correct calculation process.

4. How many centimeters are in 1 foot?

Correct answer: A

Rationale: The correct answer is A, which is 30.48. To convert inches to feet, since there are 12 inches in a foot, you need to multiply the conversion factor from inches to centimeters (2.54 cm) by the number of inches in a foot (12). This gives 30.48 cm in 1 foot. Choice B, 35, is incorrect as it does not follow the correct conversion. Choices C and D, 25 and 40 respectively, are also incorrect conversions and do not align with the conversion factors provided in the question.

5. Fred's rule for computing an infant's dose of medication is: infant's dose = (Child's age in months x adult dose) / 150. If the adult dose of medication is 15 mg, how much should be given to a 2-year-old child?

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.

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