In spite of an increase in price of a commodity by 20%, the overall expenditure on it increases by 12 %. What is the percentage decrease in the quantity of commodity consumed?

$6\frac{2}{3}$

Let the Price and expenditure = 100

            Price                    Expenditure

             100                        100

after an increase in price of 20% and in expenditure of 12%

            Price                    Expenditure

             120                        112

Expenditure must be reduced by 120 - 112 = 8

Percentage of reduction in expenditure = 8 × \(\frac{100}{120}\) = $6\frac{2}{3}$