SOLUTION: Two workers and B together could finish a work in 8 days. They worked together for 6 days and A left the work. The remaining work was completed by B alone in 6 days. How many days

Algebra ->  Equations -> SOLUTION: Two workers and B together could finish a work in 8 days. They worked together for 6 days and A left the work. The remaining work was completed by B alone in 6 days. How many days       Log On


   



Question 1067383: Two workers and B together could finish a work in 8 days. They worked together for 6 days and A left the work. The remaining work was completed by B alone in 6 days. How many days would each take to complete the work individually ?
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
What we have to find is
a= number of days that it would take worker A to complete the job by himself (or herself),
and
b= number of days needed for B to complete the job working alone.
In one day of work, the fraction of the job that
A would complete is 1%2Fa ,
and the fraction of the job B would complete
is 1%2Fb .
Working together, they would complete
1%2Fa%2B1%2Fb of the job each day,
and that would be 1%2F8 of the job.
(You could also say that
8%2A%281%2Fa%2B1%2Fb%29=1 ),
but either way, you end up with
1%2Fa%2B1%2Fb=1%2F8 .
6%2A%281%2F8%29=6%2F8=3%2F4 is the fraction of the job
that A and B complete, working together,
during the first 6 days.
6%2A%281%2Fb%29 is the fraction of the whole job
that B does all alone, during the next 6 days.
After that, the fraction of the job that has been completed is
1=3%2F4%2B6%281%2Fb%29 or 1=3%2F4%2B6%2Fb .
We solve that to find b :
Multiplying both sides of the equal sign times 4b
we get the equivalent equation
4b=3b%2B24
4b-3b=24
highlight%28b=24%29 .
Now, substituting the value for b
into 1%2Fa%2B1%2Fb=1%2F8 ,
we get 1%2Fa%2B1%2F24=1%2F8 ,
which we solve for a .
First, we multiply both sides of the equal sign
times 24a to get the equivalent equation
24%2Ba=24a%2F8
24%2Ba=3a
24=3a-a
24=2a
a=24%2F2
highlight%28a=12%29 .