<PRE><B>Question 631628</B>
Let the speed limit be x mph

First half speed = (x-5) mph
Second half speed = (x+5) mph

Half distance = 390/2 = 195 miles

24 minutes = 24/60 = 2/5 hours

time = distance/speed

First half time = 195/(x-5)

Seond half time = 195/(x+5)

{{{195/(x-5) -195/(x+5) = 2/5}}}

LCD = 5(x+5)(x-5)

Multiply equation by the LCD
{{{195*5(x+5) -195*5(x-5)= 2(x-5)(x+5)}}}

975x+4875-975x+4875 = 2(x^2-25)

9750 = 2x^2-50
2x^2= 9800
/2
x^2= 4900
take the square root
x= 70 mph

Speed limit is 70 mph

m.ananth@hotmail.ca

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