Answer:
1150 km/hr
Explanation:
Formula for Average Speed is given as = Distance in Kilometers/ Time in Hours
In the question we are given the following parameters.
The length of a planet's orbit around a star = Distance = 17,650,000 km.
Time taken to complete a full orbit = 640 Earth days
Step 1
We need to convert the time in days to hours
1 Earth day = 24 hours
640 Earth days =
We cross multiply
640 Earth days × 24 hours
= 15360 hours.
Step 2
Average Speed = Distance in Kilometers/ Time in Hours
Average Speed = 17,650,000 km. /15360 hours
Average Speed = 1149.0885417 km/hr
Approximately to 3 significant figures=
1150 km/hr
Therefore, the planets average speed in kmh-1 to 3sf is 1150 km/hr