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. Lulu is 5 years younger than her sister, who is 7 years older than their 15-year-old cousin. How old is Lulu?

Correct answer: C

Rationale: Let Lulu's sister's age be x. According to the given information, x = 15 (cousin's age) + 7 = 22. So, Lulu's sister is 22 years old. Since Lulu is 5 years younger than her sister, Lulu's age is 22 - 5 = 17. Therefore, Lulu is 17 years old. Choices A, B, and D are incorrect because they do not correspond to the calculations based on the information provided in the question.

3. A train leaves the station at 1:45 PM traveling at a constant speed of 65 mph. If it arrives at its destination at 3:15 PM, how many miles did it travel?

Correct answer: A

Rationale: To calculate the distance traveled by the train, multiply the speed (65 mph) by the time it took to reach the destination, which is 1.5 hours (3:15 PM - 1:45 PM = 1.5 hours). Therefore, 65 mph × 1.5 hours = 97.5 miles. This calculation is correct because distance = speed × time. Choices B, C, and D are incorrect as they do not reflect the correct calculation based on the given information.

4. An ancient Egyptian pyramid has a square base with side lengths of 20 meters and a remaining height (after erosion) of 10 meters. Its original height was 30 meters. What was the volume of the pyramid in its original state?

Correct answer: A

Rationale: To find the volume of a pyramid, you can use the formula: Volume = (1/3) * base area * height. In this case, the base area is the square of side length 20 meters, which is 20 * 20 = 400 square meters. The original height of the pyramid is 30 meters. Therefore, the volume of the pyramid in its original state is (1/3) * 400 * 30 = 12000 cubic meters. Choice A is correct. Choices B, C, and D are incorrect as they do not correctly calculate the volume using the original height and base area of the pyramid.

5. Multiply: 6 × 0.06 =

Correct answer: C

Rationale: When multiplying 6 by 0.06, you can treat 0.06 as 6 hundredths. So, 6 × 0.06 is equivalent to 6 × 6 hundredths, which equals 0.36. The correct answer is 0.36. Choice A (0.0036) is incorrect because it represents 6 multiplied by 0.0006, not 0.06. Choice B (0.036) is incorrect as it represents 6 multiplied by 0.06 without considering the position of the decimal point. Choice D (3.6) is incorrect as it represents 6 multiplied by 6, not by 0.06.

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