Question 655094
A jet plane, flying 30 mph faster than a propeller plane, travels 5460 miles in 1 hours less time than the propeller plane takes to fly the same distance. How fast does each plane fly?
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let x=speed of propeller plane
x+30=speed of jet plane
travel time=distance/speed
..
{{{5460/x-5460/(x+30)=1}}}
LCD:x(x+30)
5460(x+30)-5460x=x(x+30)
5460x+30*5460-5460x=x^2+30x
163800=x^2+30x
x^2+30x-163800=0
factor or solve by quadratic formula
(x+420)(x-390)=0
x=-420 (reject x>0)
or 
x=390
x+30=420
speed of propeller plane=390 mph
speed of jet plane=420 mph