Correct Answer: D

Rationale: To determine if a number is divisible by 3, we can check if the sum of its digits is divisible by 3. If the sum of the digits is divisible by 3, then the original number is also divisible by 3. A) 105: 1 + 0 + 5 = 6, which is divisible by 3. Therefore, 105 is divisible by 3. B) 141: 1 + 4 + 1 = 6, which is divisible by 3. Therefore, 141 is divisible by 3. C) 273: 2 + 7 + 3 = 12, which is divisible by 3. Therefore, 273 is divisible by 3. D) 810: 8 + 1 + 0 = 9, which is not divisible by 3. Therefore, 810 is NOT divisible by 3. Therefore, the correct answer is D (810). Choices A, B, and C are all divisible by 3 as the sum of their digits is divisible by 3.

Correct Answer: C

Rationale: To divide mixed numbers, we first convert them to improper fractions. Converting 4â…› to an improper fraction gives us 33/8, and converting 1½ gives us 3/2. Dividing 33/8 by 3/2, we multiply the first fraction by the reciprocal of the second. This gives us (33/8) / (3/2) = (33/8) * (2/3) = 66/24 = 11/4, which simplifies to 2¾. Therefore, the correct answer is 2¾. Choices A, B, and D are incorrect as they do not represent the correct result of dividing 4â…› by 1½.

Correct Answer: B

Rationale: If the team can replace 14 streetlights in 7 hours, it means they replace 2 streetlights per hour. In a 30-hour week, they can therefore replace 2 x 30 = 60 streetlights. To replace all 120 downtown streetlights, they will need 120 / 2 = 60 hours, which is equivalent to 60 / 30 = 2 weeks. Therefore, the correct answer is 2 weeks. Choice A, 1½ weeks, is incorrect because it doesn't consider the total number of streetlights that need to be replaced. Choice C, 2½ weeks, is incorrect as it overestimates the time needed. Choice D, 3 weeks, is incorrect as it underestimates the efficiency of the team in replacing streetlights.

Correct Answer: A

Rationale: The Roman numeric system does not use place value as the Arabic, Decimal, and Binary systems do. In the Roman numeral system, the value of each symbol is independent of its position, unlike in the other systems where the position of a digit affects its value. This unique characteristic of Roman numerals distinguishes them from place-value systems like Arabic, Decimal, and Binary. Therefore, the correct answer is Roman (Choice A). Choices B, C, and D (Arabic, Decimal, and Binary) all utilize place value, where the position of a digit within a number determines its value, unlike Roman numerals.

Correct Answer: B

Rationale: For every 3 parts of beans, Gus needs 5 parts of ground beef. This means the ratio of beans to beef is 3:5. If Gus is using 8 cups of ground beef, the total parts would be 3 parts beans to 5 parts beef, which is a total of 8 parts. To find out how many cups of beans Gus needs, we can set up a proportion: 3/5 = x/8. Cross multiplying gives us 5x = 24. Solving for x, we get x = 4. Therefore, Gus will need 4 cups of beans. Choice A, C, and D are incorrect as they do not align with the correct proportion calculation.