Three successive discounts of 20%, 25% and 10% on the marked price are together equivalent to a single discount of what percent?

On a marked price of 100: $100\times 0.80\times 0.75\times 0.90$ = ₹54, so ₹46 is taken off — a single discount of 46%. (Adding 20 + 25 + 10 = 55% overstates it, because each later discount is taken on an already smaller amount.)