SOLUTION: A man drives 500km to a business convention. On the return trip, he increases his speed by 25km per hour and saves 1 hour of driving time. How fast did he go in each direction?
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Question 913651: A man drives 500km to a business convention. On the return trip, he increases his speed by 25km per hour and saves 1 hour of driving time. How fast did he go in each direction? Answer by mananth(16946) (Show Source):
Distance = same 500 km 1
original time – time with increased speed = 1 hour
t=d/t
500 / x - 500 / ( x + 25 ) = 1
LCD= x ( x + 25 )
multiply by LCD
500 ( x + 25 ) - 500 x = 1 x ( x + 25 )
500 x + 12500 - 500 x = X^2 + 25 x
12500 = 1 X^2 + 25 x
X^2 + 25 x - -12500 = 0
x^2+125x-100x-12500=0
x(x+125)-100(x+125)=0
(x+100)(x+125)=0
x=100 OR -125
ignore negative
x= 100
100 & 125 km/h
