Final answer:
Not all cities have a speed limit of 30 kph (18 mph) in residential and business districts. Speed limits can vary depending on the location and regulations set by the local government.
Step-by-step explanation:
No, not all cities have a speed limit of 30 kph (18 mph) in residential and business districts. Speed limits can vary depending on the location and regulations set by the local government. While 30 kph (18 mph) is a common speed limit for residential areas, some cities may have higher or lower speed limits in different areas.