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.

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.

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: C

Rationale: Rationale: When a number is written in scientific notation as \(a \times 10^n\), the value of the number in standard form is obtained by multiplying \(a\) by \(10^n\). In this case, the number is \(4.82 \times 10^3\). To convert this to standard form, we multiply 4.82 by \(10^3\), which means moving the decimal point 3 places to the right. \(4.82 \times 10^3 = 4820\) Therefore, the value of the number in standard form is 4820, which corresponds to option C.

Correct Answer: C

Rationale: 12 - 7 & 4\5 equals 4 & 1\5.