SOLUTION: (Solve)Air Travel: A turbo-jet flies 50mph faster than a super-prop plane. If a turbo-jet goes 2000mi in 3hr less time than it takes the super-prop to go 2800mi, find the speed of

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: (Solve)Air Travel: A turbo-jet flies 50mph faster than a super-prop plane. If a turbo-jet goes 2000mi in 3hr less time than it takes the super-prop to go 2800mi, find the speed of       Log On


   

Question 563800: (Solve)Air Travel: A turbo-jet flies 50mph faster than a super-prop plane. If a turbo-jet goes 2000mi in 3hr less time than it takes the super-prop to go 2800mi, find the speed of each plane.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
prop -x mph
turbo ---x+50 mph
t=d/r
t(prop) - t(turbo) = 3
2800/x - 2000/(x+50) = 3
LCD = x(x+50)
2800(x+50)-2000x=3x(x+50)
2800x+140000-2000x=3x^2+150x
3x^2-650x-140000=0
Find the roots of the equation by quadratic formula

a= 3 b= -650 c= -140000

b^2-4ac= 422500 - 1680000
b^2-4ac= 2102500 sqrt%28%092102500%09%29= 1450
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=( 650 + 1450 )/ 6
x1= 350
x2=( 650 -1450 ) / 6
x2= -133.33
Ignore negative value
x = 350 mph speed of prop
speed of turbo = 400 mph