a and b can do a piece of work in 28 days. with the help of c, they can finish it in 21 days .how long will c take to finish it Select:  A) 84 days  B) 74 days  C) 64 days  D) 82 days  E) 86 days
84 days + B 's 1 day work = 1/28   84 days + B + C 's 1 day work = 1/21   1/28 + C= 1/21   C = 1/21 - 1/28   C = 1/84   So C ll finish the work alone in 84 days   84 daysNSWER:84 days
<result>A</result>
a and b can do a piece of work in 28 days. with the help of c, they can finish it in 21 days .how long will c take to finish it