(1) Let the original averageexpenditure of electricity bill for onestudent per day be ₹x.Sum of per day expenditure of 10students = ₹10x Sum of per day expenditure of 15students = ₹15(x–2) According to the question, 15(x–2)–10x=50 ⇒15x–30–10x=50 ⇒5x=80 ⇒x=16 ∴ Original expenditure on electricitybill per day =₹16×10=₹160