Question 580860
Jo can do a piece of work in 20 days while Paul can do it in 25 days.
 they work for 5 days, then his brother backed out.
 how many days did Jo work alone?
:
Let t = time worked alone by Jo
:
Let the completed job = 1
:
{{{((t+5))/20}}} + {{{5/25}}} = 1
Multiply by 100 to clear the denominators, results:
5(t+5) + 4(5) = 100
5t + 25 + 20 = 100
5t = 100 - 45
5t = 55
t = 55/5
t = 11 days Jo worked alone