<PRE><B>Question 214120</B>
 James and Charles working together can paint a house in 9 days. James, a faster painter, can do alone the work in 15 days.
 How long will it tale Charles to paint the house alone?
;
Let c = time required by Charles, working alone
:
Let the completed job = 1 (the painted house)
;
{{{9/15}}} + {{{9/c}}} = 1
;
Multiply equation by 15c, results
9c + 9(15) = 15c
:
9c + 135 = 15c
:
135 = 15c - 9c
:
135 = 6c
c = {{{135/6}}}
c = 22.5 days, Charles working alone
:
:
Check solution
{{{9/15}}} + {{{9/22.5}}} = 1
.6 + .4 = 1</PRE>