A and B can do a job is 16 days and 12 days respectively. 4 days before finishing the job, A joins B. B has started the work alone. Find how many days B has worked alone?
Choose the correct choice from the following answers
A) 6 days	B) 4 days	C) 5 days	D) 7 days	E) None of these
A’s one day’s work = 1⁄16 th work   B’s one day’s work 1⁄12 th work   Let B has worked alone = x days. Then,   A’s amount of work + B’s amount of work = 1   ⇒ 4(1⁄16) + (x + 4)(1⁄12) = 1   ⇒ 1/4+x+4/12 = 1 ⇒ x = 3⁄4 × 12 - 4   ⇒ x = 5 days.   Answer 5 days
<result>C</result>
A and B can do a job is 16 days and 12 days respectively. 4 days before finishing the job, A joins B. B has started the work alone. Find how many days B has worked alone?