Correct Answer: B

Rationale: To convert a percentage to a decimal, you divide the percentage by 100. Therefore, 38% as a decimal is 0.38 (38 · 100 = 0.38). Choice A, 3.8, is incorrect as it is equivalent to 380%. Choice C, 0.038, is incorrect as it represents 3.8%. Choice D, 38.0, is incorrect as it is still in percentage form.

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: 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: 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.

Correct Answer: A

Rationale: To convert a percentage to a decimal, you divide by 100. In this case, 38% divided by 100 equals 0.38. Moving the decimal point two places to the left converts the percentage to a decimal. Choice B is incorrect because it incorrectly moves the decimal point one place to the left. Choice C is incorrect as it moves the decimal point three places to the left. Choice D is incorrect as it does not convert the percentage to a decimal.