Final answer:
To find the actual distance at a given scale, multiply the segment length by the scale factor. In this case, the actual distance corresponding to a 3.2 cm segment is 640 km.
Step-by-step explanation:
To find the actual distance represented by a given segment at a scale, you need to use the scale factor. In this case, the scale is 1:20,000,000, which means that 1 cm on the map represents 20,000,000 cm or 200,000 m or 200 km in actual distance. Since the segment is 3.2 cm, we can multiply it by 200 km/cm to find the actual distance:
3.2 cm * 200 km/cm = 640 km.
Therefore, the answer is (d) 640 km.