Answer: 4 hours
Explanation:
The two planes are flying in opposite directions, so the distance between them is increasing at a rate equal to the sum of their speeds. The first plane is traveling at a speed of 450 miles per hour and the second plane is traveling at a speed of 550 miles per hour. Therefore, the relative speed of the two planes is 1000 miles per hour.
To find out how long it will take for the planes to be 4,000 miles apart, we can use the formula:
distance = rate x time
Let t be the time it takes for the planes to be 4,000 miles apart. Then we have:
4000 = 1000t
Solving for t, we get:
t = 4
Therefore, it will take 4 hours for the two planes to be 4,000 miles apart 123.