SOLUTION: a takes 4 hours more than b to walk 30km. if he doubles his speed,he takes 1hourless time than b. find the rate of walking

Question 540484: a takes 4 hours more than b to walk 30km. if he doubles his speed,he takes 1hourless time than b. find the rate of walking
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
a takes 4 hours more than b to walk 30km. if he doubles his speed,he takes 1hourless time than b. find the rate of walking
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A DATA:
distance = 30 km ; time = (x+4) hrs ; rate = 30/(x+4) km/hr
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B DATA:
distance = 30 km ; time = x hrs ; rate = 30/x km/hr
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A DATA: when speed doubled:
distance = 30 km ; rate = 60/(x+4) km/hr ; time = 30/[60(x+4)] hrs
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Equation:
B time - new A time = 1 hr
x - [30/(60(x+4)) = 1
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x - (1/(2x+8)) = 1
2x^2+8x - 1 = 2x+8
2x^2+6x-9 = 0
x = [-6 +- sqrt(36-4*2*-9)]/4
Positive solution:
x = [-6 + 10.39]/2
x = 2.12 km/hr (B's walking rate)
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Cheers,
Stan H.
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