a lab needs 200ml of a 5 salt solution they only have a 10 solution how much 10 solution and water should be mixed

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?

A. 100ml 10% solution, 100ml water
B. 150ml 10% solution, 50ml water
C. 160ml 10% solution, 40ml water
D. 200ml 10% solution, 0ml water

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. Solve for x: x/5 = 3/10.

A. x = 0.6
B. x = 0.6
C. x = 0.9
D. x = 1.5

Correct answer: D

Rationale: To solve for x when x/5 = 3/10, you need to cross-multiply. This gives you 10x = 5 Ã— 3. Simplifying further, you get x = 15/10, which reduces to x = 1.5. Therefore, the correct answer is x = 1.5. Choices A, B, and C are incorrect because they do not match the correct calculation for x.

3. Which numeric system was a base 20 system?

A. Mayan
B. Babylonian
C. Roman
D. Arabic

Correct answer: A

Rationale: The Mayan numeric system was a base 20 system, known as vigesimal, as it used base 20 numerals. This system was unique and employed a combination of symbols and positional notation to represent numbers. The Babylonian system was a base 60 system, Roman numerals were based on combinations of letters, and Arabic numerals are in base 10, making choices B, C, and D incorrect.

4. 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?

A. 2.4 hours
B. 6 hours
C. 12 hours
D. 16.4 hours

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.

5. Rectangle: A picture frame measures 15cm by 20cm. What is its perimeter?

A. 30cm
B. 55cm
C. 65cm
D. 75cm

Correct answer: C

Rationale: To find the perimeter of a rectangle, you add the lengths of all sides. The formula for the perimeter of a rectangle is 2 * (length + width). In this case, the length is 15cm and the width is 20cm. Therefore, the perimeter = 2 * (15cm + 20cm) = 65cm. Choice A (30cm), Choice B (55cm), and Choice D (75cm) are incorrect as they do not correctly calculate the perimeter of the given rectangle.