Which of the following conversion factors is a measured number?

• A. 1 inch = 2.54 cm
• B. 1 m = 100 cm
• C. 1 kg = 2.205 lb
• D. 1 cup = 237 mL

Answer: (D)

Verified step by step guidance

1. Understand the difference between measured numbers and exact numbers: Exact numbers come from definitions or counting and have no uncertainty, while measured numbers come from experimental measurements and have some uncertainty.
2. Look at the given conversion factors: 1 inch = 2.54 cm and 1 m = 100 cm are defined exactly by international agreement, so these are exact numbers.
3. The conversion 1 kg = 2.205 lb is based on measurement and experimental determination, so this is a measured number with some uncertainty.
4. The conversion 1 cup = 237 mL is also based on measurement, as the volume of a cup can vary slightly depending on the standard used, so this is a measured number.
5. Therefore, among the options, the conversion factors involving pounds and cups are measured numbers, while those involving inches and meters are exact numbers.