How long will it take the to be 2250 kilometers apart?

Question

Two planes have an airport traveling in opposite directions. One plane travels at 470 kilometers per hour and the other at 430 kilometers per hour. How long will it take the to be 2250 kilometers apart?

Answer 1

If the two planes are traveling in opposite directions, then they are traveling on a straight line with respect to each other. Therefore, their distance apart will be equal to their composite speed times the time aka:

 

distance = (total speed) * (time)

 

2250 km = (470 km/hr + 430 km/hr) * time

 

2250 km = 900 km/hr * time

 

time = (2250 km)/(900 km/hr) = 2.5 hours 

Answer 2

d = r · t

 

For one place

d = 470t

 

For the other plane

d = 430t

 

The total (cue to add) distance

2250 = 470t + 430t

2250 = 900t

2.5 = t

 

It would take 2.5 hours to be 2250 miles apart

 

Check:

 

470(2.5) + 430(2.5)

1175 + 1075

2250