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. How many gallons are in 16 quarts?

Correct answer: C

Rationale: To convert quarts to gallons, remember that 1 gallon equals 4 quarts. Therefore, 16 quarts รท 4 quarts/gallon = 4 gallons. The correct answer is 4 gallons because each gallon contains 4 quarts. Choice A (1 gallon) is incorrect because 1 gallon is equal to 4 quarts, not 16 quarts. Choice B (8 gallons) is incorrect as it miscalculates the conversion. Choice D (4.5 gallons) is incorrect because it doesn't align with the conversion rate of 4 quarts per gallon.

3. Bill has 2.5 vacation days left for the rest of the year and 1.25 sick days left. If Bill uses all of his sick days and his vacation days, how many days will he have off work?

Correct answer: D

Rationale: To find the total number of days Bill will have off, add his vacation days and sick days together. Bill has 2.5 vacation days and 1.25 sick days: 2.5 + 1.25 = 3.75 days When rounding to the nearest whole number, 3.75 rounds up to 4. Therefore, Bill will have 4 days off work.

4. A solution is 60% alcohol. If 200ml of the solution is used, how much pure alcohol is present?

Correct answer: B

Rationale: If the solution is 60% alcohol, it means that 60% of the solution is alcohol. Therefore, in 200ml of the solution, the amount of alcohol present is: 200ml * 60% = 200ml * 0.60 = 120ml. So, when 200ml of the solution is used, there are 120ml of pure alcohol present. Choice A, 100ml, is incorrect because it does not account for the correct percentage of alcohol in the solution. Choice C, 140ml, and Choice D, 160ml, are incorrect as they overestimate the amount of pure alcohol present in the solution.

5. A child's toy block is a cube with side lengths of 5cm. What is its total surface area?

Correct answer: D

Rationale: The surface area of a cube is calculated using the formula: 6 * (side length)^2. Substituting the side length of 5cm into the formula, we get: 6 * (5cm)^2 = 6 * 25cm^2 = 150 sq cm. Therefore, the total surface area of the toy block is 150 sq cm. Choices A (25 sq cm), B (50 sq cm), and C (125 sq cm) are incorrect as they do not correctly calculate the total surface area of the cube.

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