The price of cooking gas has increased by 25%. By what percent should a family reduce the use of cooking gas so as not to increase the expenditure in this account ?

20%

Price × Consumption =  Expenditure,

{If expenditure is same then Price is inversely proportional to consumption}

25% = \(\frac{25}{100}\) = \(\frac{1}{4}\)

                         Old     :     New

Price:                 4       :       5

Consumption:     5       :       4        =    1 (Reduced by)

Percentage of reduction = \(\frac{1}{5}\) × 100% = 20%