The price of rice increased by 10%. By how much should we reduce the consumption, so that the expenditure does not increase on rice?

100/11%

To keep the expenditure on rice constant,

Ratio of consumption ∝ $\frac{1}{ratio\; of\; price}$

                      Original  :    New 

Price of rice        100     :    110

Consumption      110     :    100

Percentage decrease in consumption = \(\frac{10}{110}\) x 100

                                              = 100/11%