SOLUTION: What is Amy's speed if she travels 450 miles at a certain speed. If the car had gone 15mph faster, the trip would have taken 1 hour less?

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Question 298972: What is Amy's speed if she travels 450 miles at a certain speed. If the car had gone 15mph faster, the trip would have taken 1 hour less?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
let her speed be x
she traveled 450 miles
time taken by her = 450/x
if her speed was x-15 it would have taken 450 /x + 15
450/x - 450 / x+15 = 1
450(x+15)-450x / x(x+15)=1
450x +6750-450x =x^2 +15x
x^2+15x-6750=0
x^2+90x-75x-6750=0
x(x+90)-75(x+90)=0
(x-75)(x+90)=0
x=75 a positive value which is her speed