B is twice efficient as A and A can do a piece of work in 15 days. A started the work an after a few days B joined him . They completed the work in 11 days , from the starting .For how many days did they work together ?
A =15 days , A's one day work =1/15
B = 7.5 days ( B eficency is twice as A), B's one day work =1/7.5
Work completed by A in 11days = 11/15
Remaining work =1-11/15 =4/15 (Completed by B)
Remaining work Completed by B in = 4/15 *1/7.5 = 2 days