Efficiency of Asha is 25% more then Usha and Usha takes 25 days to complete a piece of work. Asha started a work alone and then usha joined her 5 days before actual completion of the work. For how many days Asha worked alone?

Efficiency (Asha : Usha) = 5 : 4
Number of days(Asha : Usha) = 4x : 5x = 4x : 25
∴ Number of days required by Asha to finish the work alone = 4x
= 4 x 5 = 20.
Now, since Asha and Usha did work together for last 5 days = 5 x 9 = 45%
(since efficiency of Asha = 5% and Usha's efficiency = 4%)
It means Asha completed 55% work alone.
∴ No. of days taken by Asha to complete 55% work = 55/5 = 11days