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. Convert 0.25 to a fraction.

Correct answer: A

Rationale: To convert a decimal to a fraction, place the decimal value over the place value of the last digit. In this case, 0.25 can be written as 25/100. Simplifying this fraction by dividing both the numerator and denominator by 25 gives 1/4. Therefore, 0.25 expressed as a fraction is 1/4. Choices B, C, and D are incorrect as they represent different fractional values that do not correspond to 0.25.

3. A patient is prescribed 500 mg of medication, but the available tablets are 250 mg each. How many tablets should be given?

Correct answer: B

Rationale: To find out how many tablets of 250 mg are needed to reach a total of 500 mg, you divide the total prescribed dosage by the dosage per tablet. In this case, 500 mg / 250 mg per tablet = 2 tablets. Therefore, the correct answer is 2 tablets. Choice A (3 tablets) is incorrect because it would exceed the prescribed dosage. Choices C (4 tablets) and D (5 tablets) are incorrect as they would also provide more medication than needed.

4. If Kevin can wash 30 cars in 15 minutes, how many minutes will it take him to wash 100 cars?

Correct answer: A

Rationale: To find out how many minutes Kevin will take to wash 100 cars, set up a proportion: 30 cars is to 15 minutes as 100 cars is to x minutes. Cross multiplying gives 30x = 1500. Solving for x, x = 1500 / 30 = 50. Therefore, it will take Kevin 50 minutes to wash 100 cars. Choice A is correct. Choice B, C, and D are incorrect as they do not correctly calculate the time needed based on the given information.

5. A nurse works in the military hospital from 1300 to 2000. How many hours does this nurse work?

Correct answer: C

Rationale: The nurse works from 1300 to 2000, which is a 7-hour period. To calculate the hours worked, subtract the start time from the end time: 2000 - 1300 = 700, which is equal to 7 hours. Choice A, 8 hours, is incorrect as it does not reflect the actual duration. Choice B, 11 hours, is incorrect as it overestimates the hours worked. Choice D, 12 hours, is incorrect as it is also an overestimation of the hours worked.

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