Answer:
4 hours
Step-by-step :
If Sunny runs twice as fast as Moonbeam
Given the assumed data:
Sunny's speed = 12m/h
Moonbeam's speed= 6m/h
Therefore, if they run for 2 hours, Sunny would have covered 12 * 2 = 24 miles
While Moonbeam would have covered 6 *2 = 12 miles in the same 2 hours.
This given illustration shows that given that all parameters are equal, except the x2 speed of Sunny to that of Moonbeam, he would always be 2x faster than Moonbeam.
If they run for 4 hours, Sunny would have covered 12 * 4 = 48 miles
While Moonbeam would have covered 6 *4 = 24 miles in the same 4 hours.