X alone can complete a work in 18 days and Y alone can do the same work in half time of the time taken by X. Working together what part of the same work they can complete in a day ?
Answer & explanation
Correct answer: option 4
time ∝ $\frac{1}{efficiency}$
X : Y
Time 18 : 9 = 2 : 1
Efficiency 1 : 2
Let total work = 18
Efficiency of X + Y = 3
Total time taken = $\frac{total\;work}{efficiency}$
= $\frac{18}{3}$ = 6
Work done in 1 day = $\frac{1}{total\;time\;taken}$
Thus, work done in 1 day = $\frac{1}{6}$