Question 474400: I need help, here is the question, what is the answer, please, please please...
While traveling to and from a certain destination, you realized increasing your speed by 40 mph saved 4 hours on your return. If the total distance of the roundtrip was 640 miles, find the speed driven while returning.
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! While traveling to and from a certain destination, you realized increasing your speed by 40 mph saved 4 hours on your return. If the total distance of the roundtrip was 640 miles, find the speed driven while returning.
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let x=returning speed
x-40=foward speed
Travel time=distance/speed
320/(x-40)-320/x=4
LCD: x(x-40)
320x-320(x-40)=4x(x-4)
320x-320x+12800=4x^2-16x
4x^2-16x-12800=0
Use quadratic formula to solve
a=4, b=-16, c=-12800
x=[-(-16)ħsqrt((-16)^2-4*4*-12800)]/2*4
x=[16ħsqrt(205056)]8
x=(16ħ452.83)/8
x=58.60
or
x=-54.60 (reject, x>0)
ans:
Returning speed=58.60 mph
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