SOLUTION: A cyclist travels a distance of 120km from Town A to Town B at an average speed of x km/h. If he increases his speed by 1km/h, he would save 30 minutes. Find x

Question 839167: A cyclist travels a distance of 120km from Town A to Town B at an average speed of x km/h. If he increases his speed by 1km/h, he would save 30 minutes. Find x
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
A cyclist travels a distance of 120km from Town A to Town B at an average speed of x km/h. If he increases his speed by 1km/h, he would save 30 minutes. Find x
Original Time - time after speed increase = 1/2 hour

multiply the equation by 2x(x+1)
we get
2*120(x+1) -2*120*x = x(x+1)
240x+240 -240x=x^2+x
x^2+x-240=0
x^2+16x-15x-240=0
x(x+16)-15(x+16)=0
(x+16)(x-15)=0
x cannot be negative
so x=15
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