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?  Pick one:  A) 5/10  B) 9/10  C) 7/10  D) 6/10  E) 4/10
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 7/10
<result>C</result>
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?