Correct Answer: D

Rationale: To find the area of a circle, we use the formula A = πr², where r is the radius of the circle. In this case, the diameter is 9 inches, so the radius is half of the diameter, which is 4.5 inches. Substituting the radius into the formula, we get A = π(4.5)² = 20.25 πin². Therefore, the correct answer is 20.25 πin². Choices A, B, and C are incorrect because they do not correctly calculate the area using the radius of the circle.

Correct Answer: A

Rationale: Choice A represents no correlation between two variables as it states that as a student's class attendance decreases, the student's overall grade remains the same. This scenario shows no relationship between class attendance and grade. In contrast, choices B, C, and D show clear correlations between the variables mentioned. Choice B indicates a negative correlation between exercise hours and weight gain, choice C indicates a negative correlation between miles driven and gasoline in the tank, and choice D indicates a positive correlation between water intake and plant growth rate, making them all examples of correlated relationships.

Correct Answer: B

Rationale: The correct way to find the factors of a number is to identify all pairs of numbers that, when multiplied together, result in the given number. This method allows you to determine all the factors of the number. Choice A is incorrect because dividing the number by all possible numbers is not an efficient way to find its factors. Choice C is incorrect as listing all the multiples of the number does not give the factors. Choice D is unrelated to finding factors as adding the digits of a number together does not provide information about its factors.

Correct Answer: D

Rationale: To find the cost of one syringe, divide the total cost by the number of syringes: $660.00 · 55 = $12. Therefore, the cost of four syringes is 4 x $12 = $48. Choices A, B, and C are incorrect because they do not correctly calculate the cost per syringe or the total cost of four syringes.

Correct Answer: A

Rationale: To find the length of the unknown leg (a) of a right triangle, use the Pythagorean theorem: a² + 9² = 19². Substitute the known values, solve for a: a² + 81 = 361. Subtract 81 from both sides to get a² = 280. Taking the square root of 280 gives a ≈ 16.7 feet. Therefore, the correct answer is 16.7 feet. Choice B (16.0 feet) is incorrect as it does not accurately round to the nearest tenth. Choice C (17.4 feet) and choice D (8.4 feet) are incorrect as they do not match the calculated value using the Pythagorean theorem.