Correct Answer: D

Rationale: The surface area of a cylinder can be calculated using the formula: S = 2πr² + 2πrh, where r is the radius and h is the height. Substituting the values for radius (12) and height (8) into the formula: S = 2π(12)² + 2π(12)(8). S = 2π(144) + 2π(96). S = 288π + 192π. S = 480π ≈ 1507.964. Therefore, the surface area of the cylinder is approximately 1507.2 square centimeters. Choice A, 602.9 cm², is incorrect as it is significantly lower than the correct value. Choice B, 904.3 cm², is also incorrect as it does not match the calculated surface area. Choice C, 1,408.7 cm², is incorrect as it does not align with the calculated value of the surface area.

Correct Answer: C

Rationale: To find the mean time, you need to add all the times (22.33 + 22.50 + 22.50 + 22.61 + 22.71 + 22.72 + 22.83 + 23.22) and then divide by the total number of times (8). This calculation results in a mean time of 22.68 seconds. Choice A, 22.50 sec, is incorrect because it is the time of one of the runners, not the mean time. Choice B, 22.66 sec, and Choice D, 22.77 sec, are also incorrect as they are not the calculated mean of the given times.

Correct Answer: D

Rationale: To solve the equation for x, follow these steps: 2x - 7 = 3. Add 7 to both sides to isolate 2x, resulting in 2x = 10. Then, divide by 2 on both sides to find x, which gives x = 5. Therefore, the correct answer is x = 5. Choices A, B, and C are incorrect because they do not accurately solve the equation.

Correct Answer: D

Rationale: The mean number of vacuum cleaners sold per month is 31.7, the mode is 29, the median is 31, and the range is 29. The mode being equal to the range is the correct statement. Option A is incorrect because the mean (31.7) is greater than the median (31). Option B is incorrect as the mode (29) is not greater than the median (31). Option C is incorrect since the mode (29) is not less than the mean, median, or range.

Correct Answer: A

Rationale: A proportional relationship is one in which two quantities vary directly with each other. In choice A, the amount deposited per month is directly proportional to the initial deposit. The relationship can be represented as y = 125x + 150, where x is the number of months and y is the total amount in the account. Choices B and C involve additional fixed amounts or variable costs that do not maintain a constant ratio, making them non-proportional relationships. Choice D refers to a constant speed of driving, which is not a proportional relationship as it does not involve varying quantities that change in direct proportion.