Which of the following correctly expresses the relationship between millimeters and kilometers?

• A. 1 km = 1,000 mm
• B. 1 km = 100,000 mm
• C. 1 km = 1,000,000 mm
• D. 1 km = 10,000 mm

Answer: (C)

Verified step by step guidance

1. Recall the basic metric unit conversions: 1 kilometer (km) equals 1,000 meters (m), and 1 meter equals 1,000 millimeters (mm).
2. Express the relationship between kilometers and millimeters by combining these conversions: multiply the number of meters in a kilometer by the number of millimeters in a meter.
3. Write the equation: \$1\ \text{km} = 1,000\ \text{m} \times 1,000\ \text{mm/m}$.
4. Calculate the total number of millimeters in one kilometer by multiplying the two factors: \$1,000 \times 1,000$.
5. Conclude that \$1\ \text{km} = 1,000,000\ \text{mm}$, which matches the correct answer choice.