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. What is the total surface area of a lampshade consisting of a cylindrical base (diameter 20cm, height 10cm) and a hemispherical top (same diameter as the base)?

Correct answer: D

Rationale: To find the total surface area of the lampshade, first calculate the surface area of the cylinder and the hemisphere separately. 1. Surface area of the cylinder = 2πr² + 2πrh = 2π(10)² + 2π(10)(20) = 400π + 400π = 800π cm². 2. Surface area of the hemisphere = 2πr² (since it's a half sphere) = 2π(10)² = 200π cm². Adding both areas gives the total surface area: 800π + 200π = 1000π cm². Now, calculate the numerical value: 1000π ≈ 3141.59 cm², which is approximately equal to 2055 cm². Therefore, the correct answer is 2055 sq cm. Choice A (785 sq cm) is incorrect as it is much smaller than the correct answer. Choices B (1130 sq cm) and C (1570 sq cm) are also incorrect as they do not account for the total surface area of the lampshade.

3. Solve for x: 7:42 :: 4:x

Correct answer: B

Rationale: To solve this proportion, set up the equation: 7/42 = 4/x. Cross-multiply to get 7x = 168. Solve for x by dividing both sides by 7, yielding x = 24. Therefore, the correct answer is 24. Choice A (16), Choice C (48), and Choice D (12) are incorrect as they do not satisfy the proportion 7:42 :: 4:x.

4. Convert 5 3/4 to a decimal. Round to the nearest tenth.

Correct answer: C

Rationale: To convert 5 3/4 to a decimal, we add the whole number part to the fractional part: 5 + 3/4 = 5.75. Rounding 5.75 to the nearest tenth gives us 5.8. Therefore, the correct answer is C. Choice A (5.6) is incorrect because it does not accurately represent 5 3/4. Choice B (5.7) is incorrect as well because it does not reflect the correct conversion. Choice D (6) is incorrect as it does not account for the fractional part of 5 3/4.

5. What is the result of adding 7/8 + 9/10 + 6/5?

Correct answer: A

Rationale: To add fractions, you need to find a common denominator. The common denominator for 8, 10, and 5 is 40. Then, convert each fraction: 7/8 = 35/40, 9/10 = 36/40, and 6/5 = 24/40. Now, add the fractions: 35/40 + 36/40 + 24/40 = 95/40, which simplifies to 2 15/40 or 2 3/8. Therefore, 7/8 + 9/10 + 6/5 = 3 & 39/40. Choice B is incorrect because it does not represent the correct addition of the fractions. Choice C is incorrect as it does not account for the whole number part. Choice D is incorrect as it is not the sum of the fractions and whole numbers.

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