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. 4 7/8 divided by 1 1/6 equals what?

Correct answer: D

Rationale: To divide 4,7/8 by 1,1/6: Convert to improper fractions: 4,7/8 = 39/8 1,1/6 = 7/6 Divide by multiplying by the reciprocal: 39/8 × 6/7 = 234/56 Simplify: 234/56 = 117/28 or 4,5/28

3. Which of the following numbers is the largest? (0.667, 0.68, 0.6, 0.0688)

Correct answer: B

Rationale: To determine the largest number among the given decimals, compare them. 0.68 is the largest number as it is greater than 0.667, 0.6, and 0.0688. The correct answer is 0.68 because it has the highest value. The other options are smaller: 0.667 is less than 0.68, 0.6 is less than 0.68, and 0.0688 is significantly smaller than 0.68.

4. Change the decimal to a percent: 0.64 =

Correct answer: C

Rationale: To convert a decimal to a percent, multiply by 100. In this case, 0.64 × 100 = 64%. Therefore, the correct answer is C. Choice A (0.64%) is incorrect as it represents the original decimal value in percentage form. Choice B (6.4%) is incorrect as it incorrectly multiplies the decimal value by 10 instead of 100. Choice D (0.064%) is incorrect as it represents the decimal value as a fraction of 1000 instead of 100.

5. A water fountain has a spherical base with a diameter of 50cm and a cylindrical body with a diameter of 30cm and a height of 80cm. What is the total surface area of the fountain (excluding the water surface)?

Correct answer: C

Rationale: To find the total surface area of the fountain, we first calculate the surface area of the sphere and the cylinder separately. For the sphere: - Radius = Diameter / 2 = 50 / 2 = 25 cm - Surface area of a sphere = 4πr² = 4 x π x 25² = 500π cm² For the cylinder: - Radius = Diameter / 2 = 30 / 2 = 15 cm - Surface area of a cylinder = 2πrh + 2πr² = 2 x π x 15 x 80 + 2 x π x 15² = 240π + 450π = 690π cm² Total surface area = Surface area of sphere + Surface area of cylinder = 500π + 690π = 1190π cm² ≈ 5486 sq cm. Therefore, the correct answer is C. Choice A (3142 sq cm) is incorrect as it is much smaller than the correct answer. Choices B and D are also incorrect as they do not reflect the accurate calculation of the total surface area of the fountain.

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