SOLUTION: A does a work in 20 days. A did for 28 days. Then b came. They together take 76 days to complete the 7 job. Find howmany days B complete a work.

Algebra ->  Rate-of-work-word-problems -> SOLUTION: A does a work in 20 days. A did for 28 days. Then b came. They together take 76 days to complete the 7 job. Find howmany days B complete a work.       Log On


   

Question 625647: A does a work in 20 days. A did for 28 days. Then b came. They together take 76 days to complete the 7 job. Find howmany days B complete a work.

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
Rewrite to show how I understand the problem
:
A does a work in 20 days. A worked for 28 days.
Then B came. Working together, they take 76 days to complete 7 jobs.
Find how many days it takes B to complete a work.
:
let b = time for B to do one job by himself
let one completed job = 1
:
%28%2828%2B76%29%29%2F20 + 76%2Fb = 7
104%2F20 + 76%2Fb = 7
multiply by 20b
104b + 20(76) = 20b(7)
104b + 1520 = 140b
1520 = 140b - 104b
1520 = 36b
b = 1520%2F36
b = 42.22 days to do one job alone