Working alone, A can complete a certain kind of job in 3 hours. A and D, working together at their respective rates, can complete one of these jobs in 2 hours. In how many hours can D, working alone, complete one of these jobs? Pick:	A) 2	B) 4	C) 6	D) 8	E) 10
Let total time taken by D to complete the job = D   total time taken by A to complete the job = 3   Work done by A in an hour   1/A = 1/3   Working together A and D can complete the job in 2 hours   1/A + 1/D = 1/2   =&gt;1/D = 1/2 - 1/A   = 1/2- 1/3   = 1/6   =&gt; D = 6 hours   Answer 6
<result>C</result>
Working alone, A can complete a certain kind of job in 3 hours. A and D, working together at their respective rates, can complete one of these jobs in 2 hours. In how many hours can D, working alone, complete one of these jobs?