Answer:
The time it takes for a radio message to travel from a space probe on Mars to Earth when the planets are at a distance of 56 million km can be calculated using the speed of light which is about 299,792,458 meters per second.
To convert the distance from kilometers to meters, we multiply 56 million km by 1000 to get 56 x 10^6 km = 5.6 x 10^10 m.
The time it takes for a radio signal to travel from Mars to Earth is:
time = distance/speed
time = 5.6 x 10^10 m / 299,792,458 m/s
time = 187 seconds
Therefore, a radio message from a space probe on Mars would take about 187 seconds, or just over 3 minutes, to reach Earth when the planets are at a distance of 56 million km.