<PRE><B>Question 290972</B>
Susan can sort the office mail in 15 minutes but if Kathy helps, 
they can sort the mail in 8 minutes.
 How long would it take Kathy to sort the mail alone?
:
Let k = time required by Kathy to do it alone
Let the completed job = 1
;
A typical shared work equation
{{{8/15}}} + {{{8/k}}} = 1
Multiply by 15k, results:
8k + 15(8) = 15k
8k + 120  = 15k
120 = 15k - 8k
120 = 7k
k = {{{120/7}}}
k = 17.143 minutes, Kathy alone
:
:
Check solution
8/15 + 8/17.143 =
.533 + .467 = 1</PRE>