P is able to do a piece of work in 20 days and Q can do the same work in 10 days. If they can work together for 2 days, what is the fraction of work left?	Choose the correct choice from the following options:
A) 5 / 10	B) 9 / 10	C) 7 / 10	D) 6 / 10	E) 4 / 10

Rationale: "explanation : amount of work p can do in 1 day = 1 / 20 amount of work q can do in 1 day = 1 / 10 amount of work p and q can do in 1 day = 1 / 20 + 1 / 10 = 3 / 20 amount of work p and q can together do in 2 days = 2 × ( 3 / 20 ) = 3 / 10 fraction of work left = 1 – 3 / 10 = 7 / 10 answer : option c"
Answer: C