the maximum distance between the earth and mars is 378000000 km and the minimum distance is 78000000 km. When the distance is 378000000km, the amount of time for a radio signal to travel from mars to earth is how many seconds
Radio waves travel at about 300,000,000 km /s
378,000,000km / 300,000,000 km /s ≈ 1.26 s
CPhill: A minor mistake. The speed of light is about 300,000 km/sec.
378,000,000 / 300,000 =1,260 seconds, or 21 minutes.