SOLUTION: if the speed of an aeroplane is reduced by 40km per hr,it takes 20 minutes more to cover 1200km. find the speed of the aeroplane.

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: if the speed of an aeroplane is reduced by 40km per hr,it takes 20 minutes more to cover 1200km. find the speed of the aeroplane.      Log On


   



Question 1084695: if the speed of an aeroplane is reduced by 40km per hr,it takes 20 minutes more to cover 1200km. find the speed of the aeroplane.
Found 2 solutions by Boreal, MathTherapy:
Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
speed*time=distance
x is base speed of plane
x*t=1200
(x-40)(t+(1/3))=1200
so xt=xt+(1/3)x-40t-40/3
0=(1/3)x-40t-40/3; x=1200/t
0=(400/t)-40t-(40/3)
multiply by 3t
0=1200-120t^2-40t
120t^2-40t-1200=0
3t^2-t-30=0
(3t-10)(t+3)=0
t=10/3 hours, only positive root.
x*10/3=1200
10x=3600
x=360 km/h, ANSWER, and it will take 3 1/3 hours to go 1200 km
x-40=320 km/h, and it will take 3 2/3 hours (20 more minutes) to go 1200 km.

Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!

if the speed of an aeroplane is reduced by 40km per hr,it takes 20 minutes more to cover 1200km. find the speed of the aeroplane.
Correct answer: highlight_green%28matrix%281%2C4%2C+Speed%2C+%22=%22%2C+400%2C+%22km%2Fh%22%29%29
Accept no other answer!