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. If x = -2 and m = -3, evaluate: xm - 2m

Correct answer: A

Rationale: Substitute x = -2 and m = -3 into the expression: (-2) * (-3) - 2 * (-3) = 6 + 6 = 12. Therefore, the correct answer is 12. The mistake in the other choices lies in the calculation. Choice B, 6, is the result of adding the two terms instead of subtracting the second term from the first. Choice C, 8, and Choice D, 10, are also incorrect as they do not follow the correct calculation process.

3. If a horse can trot around a track twice in 10 minutes, how many times will it circle the track at that same speed in half an hour?

Correct answer: C

Rationale: If a horse can trot around a track twice in 10 minutes, it completes one circle in 5 minutes. To determine how many times it will circle the track in half an hour (30 minutes), divide the total time by the time taken for one circle: 30 minutes / 5 minutes per circle = 6 times. Therefore, the horse will circle the track 6 times at the same speed in half an hour. Choice A, 3 times, is incorrect as it does not consider the correct time taken for a single circle. Choice B, 5 times, is incorrect as it miscalculates the total number of circles within half an hour. Choice D, 10 times, is incorrect as it overestimates the number of circles the horse can complete in the given time frame.

4. A plan for a house is drawn on a 1:40 scale. If the length of the living room on the plan measures 5 inches, what is the actual length of the built living room?

Correct answer: C

Rationale: Since the scale of the plan is 1:40, this means that 1 inch on the plan represents 40 inches in reality. Therefore, the actual length of the living room can be calculated as 5 inches on the plan multiplied by the scale factor of 40, which equals 200 inches. Converting 200 inches to feet gives us 15 feet as the actual length of the built living room. Choice A (45 feet) is incorrect because it miscalculates the conversion from inches to feet. Choice B (25 feet) is incorrect as it does not consider the scale factor provided. Choice D (12 feet) is incorrect as it does not apply the correct scale factor to convert the plan's measurements to reality.

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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