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Answer

Given: We have to multiplied by 3/2 but by mistake it was multiplied by 2/3.

            So the error will be,   (3/2 - 2/3)=5/6

             Error percentage=(Error/Actual value)* 100

                                          = (5*2)/(6*3)*100

                                          =55.55 %

Answer

In the given series the pattern is 12^3-1,11^3+2,10^3-3,9^3+4,8^3+5,...

So ?=9^3+4=729+4=733