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. A table top has dimensions of 75cm by 50cm. What is its perimeter if opposite sides are equal?

Correct answer: B

Rationale: Rationale: - Given that the table top has dimensions of 75cm by 50cm. - Since opposite sides are equal, the table top can be divided into two pairs of equal sides: 75cm and 50cm. - To find the perimeter, we add up all four sides: 75cm + 50cm + 75cm + 50cm = 250cm. - However, since opposite sides are equal, we only need to consider two sides: 75cm + 50cm = 125cm. - Therefore, the perimeter of the table top is 125cm + 125cm = 150cm. - Hence, the correct answer is B) 150cm.

3. 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.

4. Evaluate the following expression: -x + y + xy, when x = 4 and y = 2.

Correct answer: B

Rationale: To evaluate the expression, substitute x = 4 and y = 2 into the expression: -4 + 2 + 4*2. Calculate each term: -4 + 2 = -2, then 4*2 = 8. Adding these results gives -2 + 8 = 6. Therefore, the correct answer is 6. Choice A (2) is incorrect as it does not consider all terms in the expression. Choice C (12) is incorrect as it miscalculates the result by failing to account for the negative sign. Choice D (8) is incorrect as it doesn't consider the negative value of the first term in the expression.

5. If x=11, solve (x+44)/2x.

Correct answer: B

Rationale: Given x=11, substitute into the expression: (11 + 44) / (2*11) = 55 / 22 = 2.5. Therefore, the correct answer is 2.5. Choice A (33) is incorrect as it does not represent the correct calculation. Choice C (13) is incorrect as it is not the result of the expression. Choice D (55/22) is incorrect as it is the same as the simplified form of the expression, not the answer to the calculation.

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