<PRE><B>Question 919595</B>
Alice can wash her car in 3 and 1/2 hours
 if Bernice helped her she can do the job in 2 hours.
 how long would it take if Bernice working alone?
:
let b = time required by Bernice working alone
let the completed job = 1
:
Each will do a fraction of the job, the two fractions add up to 1
{{{2/3.5}}} + {{{2/b}}} = 1
multiply eq by 3.5b, cancel the denominators and you have
2b + 3.5(2) = 3.5b
2b + 7 = 3.5b
7 = 3.5b - 2b
7 = 1.5b
b = 7/1.5
b = 4{{{2/3}}} hrs Bernice working alone
:
:
 you can check this for yourself, see if the equation is true
{{{2/3.5}}} + {{{2/4.6667}}} = 1
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