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. Last night at the hospital, 76 babies were born. Of the births, 45% were girls. How many boys were born last night? (Round your numbers to the nearest whole number).

Correct answer: A

Rationale: When 45% of the babies were girls, it means the remaining 55% were boys. To determine the number of boys, calculate 55% of 76, which equals approximately 41.8, rounding up to 42. Therefore, 42 boys were born last night at the hospital. Choice B, C, and D are incorrect as they do not reflect the accurate calculation of the number of boys born.

3. Rebecca is able to paint 12 pickets on her picket fence in an hour. Her fence is 72 feet long, with 2 pickets per foot. How long will it take her to paint the fence?

Correct answer: B

Rationale: Rebecca can paint 12 pickets in 1 hour, which means she can paint 12 * 2 = 24 pickets in an hour. Since the fence is 72 feet long with 2 pickets per foot, she needs to paint a total of 72 * 2 = 144 pickets. If she paints 24 pickets per hour, it will take her 144 / 24 = 6 hours to paint the entire fence. Choice A (2.4 hours) is incorrect because it does not consider the total number of pickets on the fence. Choice C (12 hours) is incorrect as it overestimates the time needed based on her painting rate. Choice D (16.4 hours) is incorrect as it miscalculates the time required to paint the entire fence.

4. How many ounces are in 2.5 gallons?

Correct answer: C

Rationale: To convert gallons to ounces, we need to know that 1 gallon is equal to 128 ounces. Therefore, 2.5 gallons would be 2.5 x 128 = 320 ounces. This makes choice C, '320 ounces,' the correct answer. Choices A, B, and D are incorrect because they do not correctly calculate the conversion from gallons to ounces.

5. What is the result of 0.003 x 4.23?

Correct answer: A

Rationale: To find the product of 0.003 and 4.23, multiply the two numbers: 0.003 x 4.23 = 0.01269. Therefore, the correct answer is A, 0.01269. Choice B, 0.01029, is incorrect as it is the result of a different calculation. Choice C, 0.01419, is incorrect because it is not the product of 0.003 and 4.23. Choice D, 0.01329, is also incorrect as it does not represent the correct multiplication result.

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