P can do a work in 10 days and Q can do the same work in 15 days. If they work on it together for 3 days, then the fraction of the work that is left is:
Answer & explanation
Correct answer: option 3
P = 10 days, Q = 15 days,
⇒ P + Q worked for 3 days = (3 + 2) x 3 = 5 x 3 = 15 units, ..(Efficiency × Days = Total work)
⇒ Remaining work = 30 - 15 = 15 units,
⇒ Fraction of work left = \(\frac{15}{30}\) = \(\frac{1}{2}\)