Let's assume the initial consumption of petrol is 100 units and the initial price of petrol is 100.
After the price goes up by 10%, the new price of petrol becomes 110.
In order to reduce the expenditure back to 100, the consumer will need to increase the consumption at the new price.
The change in consumption required can be calculated using the formula:
Change in consumption = (Change in price / Initial Price) * 100
Change in consumption = ((110-100)/100) * 100
Change in consumption = (10/100) * 100
Change in consumption = 10
So, the consumer needs to increase the consumption by 10% in order to keep the expenditure unchanged.
