First lets put the feet into yards.
There are 3 feet in 1 yard.
300 is divisible by 3, so divide 300 by 3.
300 / 3 = 100
So far we have concluded that the rocket travels 100 yards per second.
There are 60 seconds in 1 minute
We have figured out what it travels in 1 second
To figure this out we need to multiply 100 by 60
100 * 60 = 6,000
The rocket travels 6,000 yards per minute