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. Add 2/3 + 4/9.

Correct answer: C

Rationale: To add the fractions, first find a common denominator. The least common denominator between 3 and 9 is 9. Convert 2/3 to 6/9 then add 6/9 + 4/9: = 10/9

3. If the elephant weighed 3 tons, how many pounds did it weigh?

Correct answer: A

Rationale: To convert tons to pounds, you multiply by 2000 because 1 ton is equal to 2000 pounds. Therefore, 3 tons equal 3 × 2000 = 6000 pounds. The correct answer is 6000 pounds. Choice B (5000 pounds) is incorrect because it miscalculates the conversion. Choice C (3000 pounds) is incorrect as it represents the weight of 1 ton, not 3 tons. Choice D (7000 pounds) is incorrect as it overestimates the weight of 3 tons.

4. 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.

5. What is the result of adding 6 3/4 + 8 1/6?

Correct answer: A

Rationale: To add mixed numbers, first convert them to improper fractions. 6 3/4 = 27/4 and 8 1/6 = 49/6. Finding a common denominator, we get 27/4 + 49/6 = 81/12 + 98/12 = 179/12 = 14 & 11/12. Therefore, the correct answer is A. Choice B is incorrect as it does not simplify to the correct result. Choice C is in fraction form and not in mixed number form, making it incorrect. Choice D is not the correct sum of the given mixed numbers, so it is also incorrect.

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