Correct Answer: A

Rationale: To convert a decimal to a percent, you multiply by 100. In this case, 0.000026 * 100 = 0.0026%. Therefore, the correct answer is A: 0.0026%. Choices B, C, and D are incorrect because they incorrectly place the decimal point, resulting in percentages that are too large.

Correct Answer: A

Rationale: To find the sum, you add the numbers 3.7, 7.289, and 4 together. 3.7 + 7.289 + 4 equals 14.989. The correct answer is 14.989 because it includes all decimal places from the sum of the numbers provided. Choice B (5.226) is incorrect as it doesn't account for the sum of the given numbers. Choice C (15.0) is incorrect as it rounds the sum to the nearest whole number, losing the decimal precision. Choice D (5.012) is incorrect as it doesn't reflect the correct sum of the decimal numbers.

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: C

Rationale: The metric system is based on powers of 10, making calculations and conversions easier because each unit increases or decreases by a factor of 10.

Correct Answer: B

Rationale: To find the volume of the triangular shelf, first calculate the area of the triangle (1/2 * base * height) which is (1/2 * 40 * 30) = 600 sq cm. Then, multiply this area by the depth of the shelf (600 * 25) = 15000 cu cm. Therefore, the volume of each shelf is 3750 cu cm. Choice A, C, and D are incorrect as they do not correctly calculate the volume based on the dimensions provided.