Correct Answer: D

Rationale: To find 25% of a number, multiply the number by 0.25 (since 25% is the same as 25/100 or 0.25). In this case, 400 x 0.25 = 100. Therefore, 25% of 400 equals 100. Choice A, 800, is incorrect because it is the result of multiplying 400 by 2, not by 0.25. Choice B, 10,000, is also incorrect as it is significantly higher than the correct answer. Choice C, 200, is incorrect as it is the result of dividing 400 by 2, not by 0.25.

Correct Answer: A

Rationale: First, calculate how many pages the man reads per day. Since he reads two chapters a day and each chapter has 6 pages: 2 chapters/day 6 pages/chapter = 12 pages/day Now, divide the total number of pages by the number of pages he reads per day: 798 pages · 12 pages/day = 66 1/2 days Thus, it will take him 66 & 1/2 days to finish the book. Therefore, the correct answer is A. 66 & 1/2. Choices B, C, and D are incorrect as they do not correspond to the correct calculation based on the given information.

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: D

Rationale: To find 25% of a number, multiply the number by 0.25 (since 25% is the same as 25/100 or 0.25). In this case, 400 x 0.25 = 100. Therefore, 25% of 400 equals 100. Choice A, 800, is incorrect because it is the result of multiplying 400 by 2, not by 0.25. Choice B, 10,000, is also incorrect as it is significantly higher than the correct answer. Choice C, 200, is incorrect as it is the result of dividing 400 by 2, not by 0.25.

Correct Answer: D

Rationale: Cross-multiply to solve for x x: 1.2 42 = 14 x 1.242=14x 50.4 = 14 x 50.4=14x x = 50.4 14 = 3.6 x= 14 50.4 ​ =3.6