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 0.007 kilograms to grams.

Correct answer: A

Rationale: To convert kilograms to grams, you need to multiply by 1000 since there are 1000 grams in a kilogram. Therefore, 0.007 kilograms is equal to 0.007 x 1000 = 7 grams. Choice A is correct. Choice B is incorrect as it incorrectly multiplies by 10 instead of 1000. Choice C is incorrect as it incorrectly moves the decimal point one place to the right. Choice D is incorrect as it incorrectly moves the decimal point two places to the right.

3. How many more yellow balls must be added to the basket to make the yellow balls constitute 65% of the total number of balls?

Correct answer: B

Rationale: To find the total number of balls needed to make the yellow balls 65% of the total, let x be the total number of balls required. Initially, there are 15 yellow balls. The total number of balls would be 15 + x after adding more yellow balls. The equation to represent this is: (15 + x) / (15 + x) = 0.65 (since the yellow balls need to constitute 65% of the total). Solving this equation gives x = 50, indicating that 50 more yellow balls need to be added to the basket to reach the desired percentage. Choice A, C, and D are incorrect as they do not accurately represent the additional yellow balls needed to achieve the specified percentage.

4. In a local baseball team, 4 players, which represent 5% of the team, have long hair, and the rest have short hair. How many short-haired players are there on the team?

Correct answer: C

Rationale: Given that 4 players represent 5% of the team, let's denote the total number of players as x. The equation to represent this situation is 0.05x = 4. Solving for x, we get x = 80, which is the total number of players on the team. Since 4 players have long hair, the remaining players have short hair, which is 80 - 4 = 76. Therefore, there are 76 short-haired players on the team. Choices A, B, and D are incorrect as they do not consider the total number of players correctly, leading to inaccurate calculations.

5. How many milliliters are in 4 liters?

Correct answer: C

Rationale: To convert liters to milliliters, you must remember that 1 liter is equal to 1,000 milliliters. Therefore, to find out how many milliliters are in 4 liters, you multiply 4 by 1,000. This gives you a total of 4,000 milliliters in 4 liters. Choices A, B, and D are incorrect because they do not correctly convert liters to milliliters. A and B incorrectly represent 40 milliliters, which would be the result if you mistakenly multiplied by 10 instead of 1,000. Choice D is even further from the correct answer, as it suggests only 4 milliliters, which is significantly less than the actual conversion of 4 liters to milliliters.

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