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A decorative globe has a diameter of 25cm. What is its total surface area?
- A. 1570 sq cm
- B. 1963 sq cm
- C. 2513 sq cm
- D. 3142 sq cm
Correct Answer: B
Rationale: To find the total surface area of a sphere, you can use the formula: 4 * π * (radius)^2, where the radius is half the diameter. Given that the diameter is 25cm, the radius is half of that, which is 12.5cm. Substitute this value into the formula: 4 * π * (12.5cm)^2 ≈ 1963 sq cm. Therefore, the total surface area of the decorative globe is approximately 1963 sq cm. Choices A, C, and D are incorrect as they do not correspond to the correct calculation.
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Solve for x: 2 : 5 :: 64 : x
- A. 32
- B. 70
- C. 128
- D. 160
Correct Answer: C
Rationale: The symbol '::' represents a proportion in which the first pair of numbers is related to the second pair of numbers. To solve for x in the proportion 2 : 5 :: 64 : x, you can set up a proportion equation: 2/5 = 64/x. Cross-multiplying gives you 2x = 5 * 64, which simplifies to 2x = 320. Dividing both sides by 2, you get x = 160. Therefore, x = 128 is the correct answer. Choice A (32) is incorrect as it is not the result of solving the proportion equation. Choice B (70) is incorrect as it is not related to the given proportion. Choice D (160) is a common mistake made by wrongly interpreting the equation; the correct value of x is 128.
A plan for a barn is drawn on a 1:30 scale. If the width of a barn door on the plan measures 3 inches, what is the actual width of the finished door?
- A. 90 inches
- B. 10 feet
- C. 9 feet
- D. 7.5 feet
Correct Answer: B
Rationale: The scale of 1:30 means that 1 inch on the plan represents 30 inches in actual size. If the width of the barn door on the plan is 3 inches, the actual width is calculated by multiplying 3 inches by the scale factor (30), giving 90 inches. To convert inches to feet, divide by 12 (since 12 inches = 1 foot), resulting in 90 inches · 12 = 7.5 feet. Therefore, the correct answer is 10 feet (option B), not 7.5 feet. Option A (90 inches) is the result before converting to feet, option C (9 feet) is the incorrect conversion if the initial calculation was done correctly, and option D (7.5 feet) is the incorrect conversion of the initial calculation.
What is the absolute value of -7?
- A. 49
- B. 17
- C. 7
- D. 14
Correct Answer: C
Rationale: The absolute value of a number is its distance from zero on the number line, regardless of its sign. In this case, the absolute value of -7 is 7 because it is 7 units away from zero in the negative direction. Therefore, the absolute value of -7 is 7. Choice A (49) is incorrect as it is the square of -7, not the absolute value. Choice B (17) and Choice D (14) are incorrect values and do not represent the absolute value of -7.
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.
How many liters are in 120 milliliters?
- A. 1.2 liters
- B. 12 liters
- C. 1,200 liters
- D. 0.12 liters
Correct Answer: D
Rationale: To convert milliliters to liters, divide the milliliters by 1000 since there are 1000 milliliters in a liter. In this case, 120 milliliters divided by 1000 equals 0.12 liters. Therefore, the correct answer is 0.12 liters. Choice A (1.2 liters) is incorrect as it incorrectly moved the decimal point. Choice B (12 liters) is incorrect as it incorrectly multiplied by 10 instead of dividing by 1000. Choice C (1,200 liters) is incorrect as it added an extra zero, resulting in a much larger value.