A can do three times of the work done by B in one day. They together finish \(\frac{2}{5}\)th part of the work in 9 days. The number of days in which B can do the work alone is:
Answer & explanation
Correct answer: option 2
A : B : (A + B)
Efficiency: 3 : 1 : 4
ATQ,
(A + B) can do \(\frac{2}{5}\) of the work in ⇒ 9 days
(A + B) can do 01 work in ⇒ 9 × \(\frac{5}{2}\) = \(\frac{45}{2}\) days
Now, Total Work = Time × Efficiency = \(\frac{45}{2}\) × 4 = 90
B alone can do it in ⇒ \(\frac{90}{1}\) = 90 days