Two persons A and B can complete a piece of work in 30 days and 45 days respectively. If they work together, what part of the work will be completed in 5 days? Choose the correct answer:
A) 5 / 18
B) 1 / 6
C) 1 / 4
D) 1 / 9
E) 2 / 6

Rationale: "a ' s one day ' s work = 1 / 30 b ' s one day ' s work = 1 / 45 ( a + b ) ' s one day ' s work = 1 / 30 + 1 / 45 = 1 / 18 the part of the work completed in 5 days = 5 ( 1 / 18 ) = 5 / 18 . answer a"
Answer: A