A can do a piece of work in 3 hours; B and C together can do it in 3 hours, while A and C together can do it in 2 hours. How long will B alone take to do it?
Select
A) 12  B) 9  C) 8  D) 6  E) 5

Rationale: "a ' s 1 hour ' s work = 1 / 3 ; ( b + c ) ' s 1 hour ' s work = 1 / 3 ; ( a + c ) ' s 1 hour ' s work = 1 / 2 . ( a + b + c ) ' s 1 hour ' s work = ( 1 / 3 + 1 / 3 ) = 2 / 3 . b ' s 1 hour ' s work = ( 2 / 3 - 1 / 2 ) = 1 / 6 . therefore a alone will take 6 hours to do the work . d"
Answer: D