Correct Answer: C

Rationale: To find the difference between 15.7 and 9.8, you need to subtract 9.8 from 15.7. This operation results in 5.9. Therefore, the correct answer is 5.9. Choice A, 6.1, is incorrect as it represents the result of subtracting 9.8 from 15.9, not 15.7. Choice B, 8.96, is also incorrect as it is not the correct result of the subtraction provided. Choice D, 4.30, is incorrect as well, as it is not the result of subtracting 9.8 from 15.7.

Correct Answer: B

Rationale: To solve this proportion, set up the equation: 7/42 = 4/x. Cross-multiply to get 7x = 168. Solve for x by dividing both sides by 7, yielding x = 24. Therefore, the correct answer is 24. Choice A (16), Choice C (48), and Choice D (12) are incorrect as they do not satisfy the proportion 7:42 :: 4:x.

Correct Answer: C

Rationale: To convert a fraction to a decimal, divide the numerator by the denominator. In this case, 5 · 8 = 0.625. Therefore, the correct answer is 0.625. Choice A (0.7) is incorrect as it represents 7/10, choice B (0.325) is incorrect as it represents 325/1000, and choice D (5.8) is incorrect as it is not the result of dividing 5 by 8.

Correct Answer: B

Rationale: To convert from Celsius to Fahrenheit, use the formula: F = (C 9/5) + 32. Substituting 50°C: F = (50 9/5) + 32 = 122°F. Therefore, 50°C is approximately 122°F. Choices A, C, and D are incorrect because they do not reflect the accurate conversion of 50°C to Fahrenheit.

Correct Answer: A

Rationale: To find the sum of 4.934, 7.1, and 9.08, we add them together: 4.934 + 7.1 + 9.08 = 21.114. Therefore, the correct answer is A, 21.114. Choice B, 21.042, is incorrect as it does not represent the accurate sum of the numbers provided. Choice C, 20.214, is incorrect as it does not account for the correct addition of the given numbers. Choice D, 59.13, is incorrect as it is not the sum of the numbers 4.934, 7.1, and 9.08.