A number is decreased by 35% and then increased by 40%. The number so obtained is 81 less than the original number. What was the original number?

900

             Actual No.   :    New No.      

-25%             20        :       13

+25%            5        :       7

Total Effect   100      :     91    ⇒    9 (decrease)

         9 unit = 81(Given)

         1 unit = 9

    Original no. is = 100 Units = 100 × 9 = 900