Speed = Distance / time
Distance = Speed x time
In t hours, first plane travels = 600 t miles
In t hours, the second plane travels =150 t miles
After t hours the distance between the two planes is:
(600t+150t)= 750t ( since both travel in opposite directions)
When the distance is 900 miles:
750t= 900
Solve for t:
t= 900/750
t= 1.2 hours
After 1.2 hours.
1.2 x 60 = 72 minutes = 60 +12 = 1 hour and 12 minutes
Since both leave at 10 pm:
10am + 1 hour and 12 minutes : 11:12 am
They will be 900 miles apart at 11:12 am
Each one traveled:
Plane 1:
Distance: Speed x time = 600 mph x 1.2 = 720 miles
Plane 2:
Distance = Speed x time = 150 mph x 1.2 = 180 miles
