Correct Answer: D

Rationale: To make one cake, you need 2½ cups of flour. To make 6 cakes, you would need 6 times the amount of flour for one cake, which is 2½ x 6 = 15 cups. Therefore, the correct answer is 15 cups. Choices A, B, and C are incorrect as they do not correctly calculate the total amount of flour needed for 6 cakes.

Correct Answer: A

Rationale: To find the volume of a pyramid, you can use the formula: Volume = (1/3) * base area * height. In this case, the base area is the square of side length 20 meters, which is 20 * 20 = 400 square meters. The original height of the pyramid is 30 meters. Therefore, the volume of the pyramid in its original state is (1/3) * 400 * 30 = 12000 cubic meters. Choice A is correct. Choices B, C, and D are incorrect as they do not correctly calculate the volume using the original height and base area of the pyramid.

Correct Answer: C

Rationale: To simplify the expression -5 - (-6), we can rewrite it as -5 + 6 (since subtracting a negative number is equivalent to adding its positive counterpart). This gives us -5 + 6 = 1. Therefore, the correct answer is 1. Choice A, ½, is incorrect because the subtraction of a negative number results in a positive number. Choices B and D are also incorrect as they do not match the simplified result of -5 - (-6), which is 1.

Correct Answer: A

Rationale: To determine the initial amount she had, we subtract the amount spent ($18) from the total amount she had after spending. If she had $1,070 after spending, subtracting $18 gives us $1,052, which was the initial amount. Choices B, C, and D are incorrect as they do not consider the subtraction of the amount spent to find the initial amount.

Correct Answer: C

Rationale: Let X be Bai Lin's monthly paycheck. From the given information, she puts 10% of X in savings and spends 30% on living expenses. This means she retains 60% (100% - 10% - 30%) of her paycheck, which equals $1,545. Therefore, 60% of X is $1,545. To find X, we divide $1,545 by 60% (or 0.60), which gives us X = $2,575. Hence, Bai Lin's monthly paycheck is $2,575. Therefore, the correct answer is $2,575. Choices A, B, and D are incorrect because they do not match the calculated monthly paycheck based on the given percentages and remaining amount.