A can do a work in 20days, B in 30days. A alone start the work after 10days he left work. In how many days B can finish the work?  Pick one:  A) 30days  B) 25days  C) 20days  D) 10days  E) 15days
10days work of A = 10/20 = 1/2   remaining work = 1-1/2 = 1/2   B can finish 1/2 work = 30*1/2= 
<gadget id="calculator">30*1/2</gadget>
<output>15</output>
15days   Answer is 15days
<result>E</result>
A can do a work in 20days, B in 30days. A alone start the work after 10days he left work. In how many days B can finish the work?