P and Q can complete a work in 15 days and 10 days respectively. They started the work together and then Q left after 2 days. P alone completed the remaining work. The work was finished in --- days.
Choose the correct choice from the following answers:
A) 10
B) 11
C) 13
D) 12
E) 15
Work done by P in 1 day = 1/15   Work done by Q in 1 day = 1/10   Work done by P and Q in 1 day = 1/15 + 1/10 = 1/6   Work done by P and Q in 2 days = 2 × (1/6) = 1/3   Remaining work = 1 – 1/3 = 2/3   Time taken by P to complete the remaining work 2/3 = (2/3) / (1/15)= 
<gadget id="calculator">(2/3) / (1/15)</gadget>
<output>10</output>
10 days   Total time taken= 2 + 10= 
<gadget id="calculator">2 + 10</gadget>
<output>12</output>
12 days   Answer is 12.
<result>D</result>
P and Q can complete a work in 15 days and 10 days respectively. They started the work together and then Q left after 2 days. P alone completed the remaining work. The work was finished in --- days.