X and Y together can finish a piece of work in 15 days, while Y alone can finish it in 40 days. X alone can finish the work in:
Answer & explanation
Correct answer: option 1
X + Y = 15 days,
Y = 40 days,
⇒ X + Y = 8, (Efficiency)
⇒ X + 3 = 8,
⇒ X = 5,
⇒ Time required by X to complete the work alone = \(\frac{120}{5}\) = 24 days, ..(\(\frac{Work}{Efficiency}\) = Time)