Final answer:
Before 1970, travelers from Sydney to Perth needed to change trains three times due to different rail gauges.
Step-by-step explanation:
Traveling from Sydney to Perth prior to 1970 required three train changes due to rail gauge differences. At that time, Australia's railway system was composed of three different gauges: the narrow gauge, the standard gauge, and the broad gauge. As passengers traveled across the country, they needed to switch trains whenever they encountered a different gauge track. This was commonly referred to as the 'break-of-gauge' and made long-distance train travel in Australia quite cumbersome.