SOLUTION: During the first part of a canoe trip, Ken covered 60 km at a certain speed. He then traveled 24 km at a speed that was 4 km/h slower. If the total time for the trip was 8 hr, what

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Question 730994: During the first part of a canoe trip, Ken covered 60 km at a certain speed. He then traveled 24 km at a speed that was 4 km/h slower. If the total time for the trip was 8 hr, what was the speed on each part of the trip?
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
First Part 60 km
Second Part 24 km

First Part x mph
Second Part x -4 mph
Total time 8 hours
First Part time 60 / x
Second Part time 24 / ( x -4 )

Time first part + time second part = 8 hours

60 / x + 24 /(x -4 ) = 8
LCD = ( x)* (x -4 )
multiply the equation by the LCD
we get
= 8
60 x -240 + )+ 24 x = 8 X^2 -32 x
116 x-240 = 8 X^2 = 0
8 X^2 -116 x+ 240 = 0
8 X^2+ -116 x+ 240 =
/ 8
8 X^2 -116 x+ 240 =0

Find the roots of the equation by quadratic formula

a= 8 b= -116 c= 240

b^2-4ac= 13456 - 7680
b^2-4ac= 5776 sqrt%28%095776%09%29= 76 OK 5
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29 )/
x1=( 116 + 76 )/ 16
x1= 12
x2=( 116 - 76 )/ 16
x2= 2.5
Ignore 2.5
x = 12 kph