Prerna decided to donate 15% of her salary to an orphanage. On the day of donation she changed her mind and donated Rs 1896, which was 80% of what she had decided earlier. How much is Prerna's salary ?
Three pipes A, B and C can fill a cistern in 36 minutes. After working together for 12 minutes, C is closed and A and B fill the cistern in 48 minutes. Find the time in which the cistern can be filled by pipe C.