9 lei initial
ieftinire cu 10% = 9-10*9/100=9-90/100=9-0.9=8.1
scumpire cu 10%= 8.1+8.1*10/100=8.1+81/100=8.1+0.81=8.91
scumpire succesiva 1: 8.91+10*8.91/100=8.91+0.891=9.801
scumpire succesiva 2: 9.801+10*9.801/100=9.801+0,9801=10,7811
ieftinire 10%=10,7811-10*10,7811/100=10,7811-1,07811=9,70299
urmata de
scumpire 10%=9,70299+10*9,70299/100=9,70299+0,970299=10,673289