Correct Answer: A

Rationale: To change a fraction into a ratio, you replace the fraction bar (/) with a colon (:). Therefore, 19/40 as a ratio is written as 19:40. Choice B (40:19) is incorrect as it reverses the order of the numbers. Choice C (19:4) is incorrect as it uses the denominator as the second number, which is not the correct way to represent a ratio. Choice D (40:4) is incorrect as it does not reflect the original fraction accurately.

Correct Answer: A

Rationale: To solve x:15=120:225, set it up as a proportion: x/15 = 120/225. Simplify the right-hand side: 120/225 = 8/15. Now, solve for x by cross-multiplying: x = 8. Therefore, the correct answer is A. Choices B, C, and D are incorrect as they do not align with the correct calculations.

Correct Answer: A

Rationale: To convert centimeters to inches, divide the measurement in centimeters by 2.54 (since 1 inch = 2.54 cm). Therefore, 65.4 cm · 2.54 = 25.74 inches. This means that the model's waist measurement of 65.4 centimeters is equivalent to 25.74 inches. Choices B, C, and D are incorrect as they do not result from the correct conversion calculation.

Correct Answer: A

Rationale: Substitute x=11 into the expression: 11 + (44 / 2*11) = 11 + (44 / 22) = 11 + 2 = 13 Therefore, the correct answer is 13. Choice A (2.5) is incorrect as the correct result is 13, not 2.5. Choice B (33) is incorrect because it does not result from the given expression. Choice C (55) is incorrect as it does not match the calculated value. Choice D (13) is incorrect because the correct solution is 13, not 2.5.

Correct Answer: A

Rationale: To add mixed numbers, first convert the fractions to a common denominator. The least common denominator between 8 and 12 is 24. Converting 7 1/8 to 7 3/24 (since 1/8 = 3/24) and 2 4/12 to 2 8/24 (since 4/12 = 8/24), we can add the whole numbers separately to get 9. Then, adding the fractions 3/24 and 8/24 gives 11/24. Therefore, 7 1/8 + 2 4/12 equals 9 11/24. Choice A is correct. Choices B, C, and D are incorrect as they do not reflect the correct addition of mixed numbers with the appropriate conversion of fractions.