A can do a piece of work in 10 days. He works at it for 4 days and then B finishes it in 9 days. In how many days can A and B together finish the work?  Options
A) 6 days B) 8 days C) 5 days D) 3 days E) 4 days
4/10 + 9/x = 1 =&gt; x = 15   1/10 + 1/15   = 1/6   =&gt; 6 days   6 daysnswer:6 days
<result>A</result>
A can do a piece of work in 10 days. He works at it for 4 days and then B finishes it in 9 days. In how many days can A and B together finish the work?