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. Subtract 20.7 - 13.4.

Correct answer: C

Rationale: The correct answer is 7.3. To subtract 13.4 from 20.7, you align the decimal points and subtract each place value: 0.7 - 0.4 = 0.3, and 2 - 1 = 1. Therefore, 20.7 - 13.4 = 7.3. Choices A, B, and D are incorrect because they do not provide the accurate result of this subtraction.

3. A lampshade is shaped like a frustum of a cone, with base diameters of 20cm and 10cm and a height of 15cm. What is its volume?

Correct answer: C

Rationale: To find the volume of the frustum of a cone, divide it into two cones and calculate their volumes separately. The formula for the volume of a cone frustum involves the radii of both bases and the height. The volume of the frustum cone can be calculated as V = 1/3 * π * h * (R^2 + r^2 + R * r), where R is the larger radius, r is the smaller radius, and h is the height. Substituting the values, V = 1/3 * π * 15 * (10^2 + 20*10 + 20^2) = 1875 cu cm. Therefore, the correct answer is 1875 cu cm. Choice A, B, and D are incorrect as they do not correspond to the correct calculation of the frustum's volume.

4. In your class, there are 48 students; 32 students are female. Approximately what percentage are male?

Correct answer: A

Rationale: In a class of 48 students, with 32 being female, the number of male students is 48 - 32 = 16. To calculate the percentage of male students, divide the number of male students (16) by the total number of students (48) and then multiply by 100 to get the percentage: (16 / 48) * 100 = 33%. Therefore, approximately 33% of the students in the class are male. Choices B, C, and D are incorrect because they do not reflect the correct calculation based on the given information.

5. How many pounds are in 176 ounces?

Correct answer: D

Rationale: To convert ounces to pounds, you divide the number of ounces by 16 since there are 16 ounces in a pound. Therefore, 176 ounces ÷ 16 = 11 pounds. Choice A is incorrect because it miscalculates the conversion. Choices B and C are also incorrect as they do not accurately convert the given ounces to pounds.

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