The tank-full petrol in Arun's motor-cycle lasts for 10 days. If he starts using 25% more every day, how many days will the tank-full petrol last?

Correct Option

Let the total volume of petrol in the tank be 'V' units.

Given that the petrol lasts for 10 days, the original daily consumption rate is V/10 units per day.

If daily consumption increases by 25%, the new daily consumption rate will be:

Original daily consumption × (1 + 0.25) = (V/10) × 1.25 = 1.25V/10 units per day.

To determine how many days the tank-full petrol will last with the new consumption rate, divide the total volume by the new daily consumption rate:

Number of days = V / (1.25V/10) = V × (10 / 1.25V) = 10 / 1.25 = 8 days.

Incorrect Options

Options 1 (5), 2 (6), and 3 (7) are incorrect. The calculation, based on a 25% increase in daily petrol consumption, precisely yields 8 days as the duration for which the tank-full petrol will last. These alternative values do not correspond with the correct mathematical derivation.