First, we convert the seconds to hours
1 hour = 60 minutes = 60 * 60 seconds = 3,600 seconds
1 hour has 3,600 seconds
If the rocket moves 4.9 miles in a second, in 3,600 seconds , it moves = 3,600*4.9 = 17,640 miles
So, in 1 hour the rocket moves 17,640 miles.
We have been given that 1 mile = 1.6 kilometers
So, 17,640 miles = 17,640*1.6 = 28,224 kilometers
So the rocket moves at a speed of 28,224 kilometers/hour