They don't need gas because satellites rotate around the world using our planet's gravitational force as centripetal force. That as well as since there is no air in space, it doesn't have to work against air resistance. This way it doesn't lose energy by going around and around the Earth.
Hope this helps, have a BLESSED day! :-)
Answer:
340 seconds = 5.667 minutes
Explanation:
As we know, S = v t or t = S / v (S = 51 x 10^9 m and v = 3 x 10^8 ms^-1)
So, t = 51 x 10^9 / 3 x 10^8 = 17 x 10^1 = 170 s
For a RTT estimation, the time span will be doubled of one way propagation for transmission and receive delay.
The over all round trip time will be = 170 x 2 = 340 seconds = 5.667 minutes
