A can do a piece of work In 14 days while 13 can do it In 21 days. They began together and worked at It for 6 days. Then. A fell ill and B had to complete the remaining work alone. In how many days was the work completed?
A's 1 day's work =114
B's 1 day's work =121
A and B's 1 day's work =114+121=3+242=542
A and B's 6 days work =542×6=57
Remaining work =1−57=27
B will finish 27 work in =27×21=6 day ∴ The whole work will finish in =6+6=12 days