SOLUTION: When Ace Airlines changed to planes that flew 100 km/h faster than its old ones, the time of its 2800 km Dallas-Seattle flight was reduced by 30 min. Find the speed of the new pla

Question 366839: When Ace Airlines changed to planes that flew 100 km/h faster than its old ones, the time of its 2800 km Dallas-Seattle flight was reduced by 30 min. Find the speed of the new planes.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
When Ace Airlines changed to planes that flew 100 km/h faster than its old ones, the time of its 2800 km Dallas-Seattle flight was reduced by 30 min. Find the speed of the new planes.
speed of 0ld plane be x
..
old plane time to seattle = 2800/x
new plane time to seattle = 2800/(x+100)
time reduction 1/2 hour
...
2800/x - 2800/(x+100)= 1/2
2800(x+100)-2800x/(x(x+100)= 1/2
2800x+280000-2800x= 1/2*(x*(x+100))
280000=1/2(x^2+100)
560000= x^2+100
x^2= 560000-100
x^2=559900
squareroot
x= 748.2 km/h
new plane speed = 748+100 = 848 km/h.
m.ananth@hotmail.ca
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