SOLUTION: A and B together can finish a piece of work in 12 days. it A alone can finish the same work in 20 days, in how many days B alone can finish it?

Algebra ->  Linear-equations -> SOLUTION: A and B together can finish a piece of work in 12 days. it A alone can finish the same work in 20 days, in how many days B alone can finish it?      Log On


   

Question 896108: A and B together can finish a piece of work in 12 days. it A alone can finish the same work in 20 days, in how many days B alone can finish it?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
A and B together can finish a piece of work in 12 days.
it A alone can finish the same work in 20 days,
in how many days B alone can finish it?
:
let b = time required by B alone to do the job
Let the completed job = 1
:
Each will do a fraction of the job, the two fractions add up to 1
:
12%2F20 + 12%2Fb = 1
multiply equation by 20b, cancel the denominators and you have
12b + 20(12) = 20b
240 = 20b - 12b
240 = 8b
b = 240/8
b = 30 hrs alone
:
:
Check this on your calc: enter (12/20) + (12/30)