Question 831537: A jet plane, flying 120 mph faster than a propeller plane, travels 4320 miles in 3 hours less time than the propeller plane takes to fly the same distance. How fast does each plane fly?
Answer by Menjax(62)   (Show Source):
You can put this solution on YOUR website! A jet plane, flying 120 mph faster than a propeller plane, travels 4320 miles in 3 hours less time than the propeller plane
takes to fly the same distance. How fast does each plane fly?
Step 1: Gather all the information in a comprehensive way.
Let S = the speed of the propeller plane. (mph)
Let T = the time it takes for the jet plane to reach it's destination.
Jet plane speed = S+120 (mph)
Jet plane distance = 4320 (miles)
Jet plane Time taken = T (hours)
Propeller plane speed = S
Propeller plane distance = 4320 (miles)
Propeller plane Time taken = T+3
(Find S and S+120)
Step 2: The key formula is Speed = Distance/Time
so S+120=4320/T [equation 1]
and S=4320/T+3 [equation 2]
ST + 3S = 4320 [equation 3]
ST + 120T = 4320 [equation 4]
solving the quadratic simultanious equations, Since s and t are positive,
S=360 and T=9
so the speed of the propeller plane is 360mph
and the speed of the jet plane is 480mph
|
|
|
