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. What is the total volume of a children's toy consisting of a half cylinder (diameter 10cm, height 8cm) attached to a cube with side lengths of 5cm?

A. 125 cu cm
B. 200 cu cm
C. 275 cu cm
D. 350 cu cm

Correct answer: C

Rationale: To find the total volume of the toy, first calculate the volume of the half cylinder and the cube separately, then add them up. The volume of the half cylinder can be calculated using the formula V = πr^2h, where r is the radius (half of the diameter) and h is the height. Substituting the values, we get V = π(5^2)8 = 200π ≈ 628.32 cubic cm. The volume of the cube is found by V = s^3, where s is the side length. Substituting s = 5, we get V = 5^3 = 125 cubic cm. Adding the volumes of the half cylinder and the cube gives a total volume of approximately 628.32 + 125 = 753.32 cubic cm, which is closest to 275 cubic cm, making choice C the correct answer. Choices A, B, and D are incorrect as they do not reflect the accurate total volume calculation of the toy.

3. Which numeric system does not use place value?

A. Roman
B. Arabic
C. Decimal
D. Binary

Correct answer: A

Rationale: The Roman numeric system does not use place value as the Arabic, Decimal, and Binary systems do. In the Roman numeral system, the value of each symbol is independent of its position, unlike in the other systems where the position of a digit affects its value. This unique characteristic of Roman numerals distinguishes them from place-value systems like Arabic, Decimal, and Binary. Therefore, the correct answer is Roman (Choice A). Choices B, C, and D (Arabic, Decimal, and Binary) all utilize place value, where the position of a digit within a number determines its value, unlike Roman numerals.

4. What number is 6 equal to 15% of?

A. 0.9
B. 40
C. 80
D. 90

Correct answer: B

Rationale: To find the number that 6 is equal to 15% of, we set up the equation 0.15x = 6, where x is the unknown number. To solve for x, we divide 6 by 0.15, which gives us x = 40. Therefore, 6 is equal to 15% of the number 40. Choice A (0.9) is incorrect as it is not the result of dividing 6 by 0.15. Choices C (80) and D (90) are incorrect as they do not satisfy the equation 0.15x = 6.

5. What is the result of adding 7/21 + 10/21?

A. 17/21
B. 15/21
C. 9/21
D. 10/21

Correct answer: A

Rationale: When adding fractions with the same denominator, you simply add the numerators while keeping the denominator the same. In this case, 7/21 + 10/21 = 17/21. Therefore, the correct answer is A. Choice B (15/21) is incorrect because it adds the numerators incorrectly. Choice C (9/21) is incorrect as it does not reflect the sum of the fractions provided. Choice D (10/21) is also incorrect as it does not represent the correct sum of the two fractions.