SOLUTION: 2800 km trip New plane flies 100 km faster Trip time reduced 30 minutes What is speed of new plane?

Question 377396: 2800 km trip
New plane flies 100 km faster
Trip time reduced 30 minutes
What is speed of new plane?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
distance = 2800 km
let speed of plane be x
time taken = 2800/x
...
New plane speed = x+100
time= 2800/(x+100)
2800/x - 2800/(x+100)= 1/2
..
LCD = x(x+100)
(
cross multiply
..
2(2800x+280000-2800x)=x(x+100)
2*280,000=x^2+100x
x^2+100x-560,000 =0
x^2+800x-700x-560,000=0
x(x+800)-700(x+800)=0
(x+800)(x-700)=0
x=-800
OR x= 700
..
The speed of new plane = 700+100 = 800 kmph
...
m.ananth@hotmail.ca
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