Question 460609
it takes kevin 3 hours more than john to paint a fence. together they painted for 3 hours, than kevin left and john finished the job in one additional hour. find how long it would take each boy to paint the fence alone?
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let x= hrs John takes to finish the job alone
1/x=John's work rate
x+3 =hrs Kevin takes to finish the job alone
1/(x+3)=Kevin's work rate
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Kevin worked for 3 hours
John worked for 4 hours
3/(x+3)+4/x)=100%=1
LCD:x(x+3)
3x+4x+12=x(x+3)=x^2+3x
x^2-4x-12=0
(x-6)(x+2)=0
x=6
or
x=-2 (reject,x>0)
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ans:
John takes 6 hrs to paint the fence alone
Kevin takes 9 hrs to paint the fence alone