SOLUTION: An airplane travels 400km at a certain speed. One year later, the same airplane does the same trip at a speed 50km/hr faster than a year ago, and it takes one hour less time. What
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Question 415647: An airplane travels 400km at a certain speed. One year later, the same airplane does the same trip at a speed 50km/hr faster than a year ago, and it takes one hour less time. What was the speed of the airplane one year ago Answer by mananth(16946) (Show Source):
Distance = same 400km
original time – time with increased speed =1hour
t=d/t
400/x-400/(x+400 )=1
LCD= (x+ 400)
multiply by LCD
400(x+400)-400x =x(x+400 )
400x+160000-400x =1X^2+400x
160000=X^2+400x
X^2+400x-160000 =0
solve using quadratic formula
a= 1 , b = 400 , c ==-160000 .
b^2-4ac=800000
x1= 247.21
x2 is negative so ignore
original speed = 247.21 mph
after one year speed= 297.21 mph
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