what is the average speed of each plane?

Question

 2 planes leave same place, 1 travels 2x faster than other, after 3.5 hrs they are 360 miles apart, what is average speed of each plane?

Answer 1

distance = rate x time

 

R is the speed of the slower plane

2R is the speed of the faster plane

 

360 = (R+2R)*3.5

 

360 = 3r*3.5

 

360 = 10.5*R

 

360/10.5 = R

 

R = 360/1 divided by 21/2

 

   = 360/1 * 2/21 = 720/21 = 240/7 = 34 and 2/7

 

 

The fast plane is 2 * 240/7 = 480/7 = 68 and 4/7 

 

together they travel at a combined speed of 102 and 6/7 mph = 720/7

 

720/7 * 3.5 = 720/7 * 7/2 = 720/2 = 360.

 

Those are slow planes.