P is 10% more efficient than Q. P can complete a work in 21 days. If P and Q work together, how many days will it take to complete the same work? Choose the correct choice from the following choices:
A) 7	B) 9	C) 11	D) 13	E) 15
The work done by P in 1 day = 1/21   Let work done by Q in 1 day = q   q × (110/100) = 1/21   q = 100/(21×110) = 10/(21×11)   The work done by P and Q in 1 day = 1/21 + 10/(21×11) = 21/(21×11)= 1/11   P and Q together can do the work in 11 days.   The answer is 11.
<result>C</result>
P is 10% more efficient than Q. P can complete a work in 21 days. If P and Q work together, how many days will it take to complete the same work?