A and B can do a work in 10 days and 15 days respectively. A starts the work and B joins him after 5 days. In how many days can they complete the remaining work?
Choose one:
A) 6 days  B) 2 days  C) 8 days  D) 4 days  E) 3 days
Work done by A in 5 days = 5/10 = 1/2   Remaining work = 1/2   Work done by both A and B in one day = 1/10 + 1/15 = 5/30 = 1/6   Remaining work = 1/2 * 6/1= 
<gadget id="calculator">1/2 * 6/1</gadget>
<output>3</output>
3 days.   Answer: 3 days
<result>E</result>
A and B can do a work in 10 days and 15 days respectively. A starts the work and B joins him after 5 days. In how many days can they complete the remaining work?