Question 1200493
<font color=black size=3>
kph = kilometers per hour


Let's call the planes A and B.


Plane A travels east at 192 kph
Plane B travels east at 960 kph, taking off 2 hours later.


A = slower plane
B = faster plane


x = amount of time the faster plane is in the air.


The slower plane got a 2 hour head start, so x+2 represents the number of hours the slower plane is flying.


Plane A
distance = rate*time
distance = 192*(x+2)


Plane B
distance = rate*time
distance = 960*x


The faster plane passes the slower one when the two aircraft have traveled the same distance.
distanceA = distanceB
192*(x+2) = 960x
192x+384 = 960x
384 = 960x-192x
384 = 768x
x = 384/768
x = 0.5


This leads to x+2 = 0.5+2 = 2.5


Plane A is in the air for 2.5 hrs (aka 2.5*60 = 150 min, aka 2 hrs + 30 min)
Plane B is in the air for 0.5 hrs (aka 0.5*60 = 30 min)


Check:
plane A's distance = 192*2.5 = 480 km
plane B's distance = 960*0.5 = 480 km
Both have traveled the same distance, so the answer is confirmed.



Answer: <font color=red>0.5 hours</font> aka <font color=red>30 minutes</font>
</font>