A CAN FINISH A WORK IN 21 DAYS AND B CAN DO THE SAME WORK IN15 DAYS. B WORKED FOR 10 DAYS AND LEFT THE JOB. IN HOW MANY DAYS, A ALONE CAN FINISH THE REMAINING WORK?	Pick one
A) 6
B) 5
C) 5.5
D) 7
E) 8

Rationale: "b ' s 10 day ' s work = ( 1 x 10 ) = 2 . 15 3 remaining work = ( 1 - 2 ) = 1 . 3 3 now , 1 work is done by a in 1 day . 21 therefore 1 work is done by a in ( 21 x 1 ) = 7 days . d"
Answer: D