To do a certain work, the ratio of efficiencies of X and Y is 5 : 7. Working together, X and Y can complete the same work in 70 days. X alone started the work and left after 42 days. Y alone will complete the remaining work in:
Answer & explanation
Correct answer: option 1
Given,
X : Y
Efficiency 5 : 7
⇒ X + Y in 70 days complete the whole work = (5 + 7) x 70 = 840 units ..(Efficiency × Days = Total work)
⇒ X left after 42 days = 5 x 42 = 210 units,
⇒ Remaining work = 840 - 210 = 630 units,
⇒ Time taken by Y to complete the remaining work = \(\frac{630}{7}\) = 90 days. ..(\(\frac{Work}{Efficiency}\) = Time)