A full tank of petrol in Arun’s motorbike lasts 10 days. If he starts using 25% more petrol per day, for how many days will the same full tank last now?

Introduction / Context:
This is an inverse-variation question. If daily consumption rises by a certain percentage, the number of days the fixed quantity lasts falls in inverse proportion.

Given Data / Assumptions:

• Original duration = 10 days.
• New daily use = 25% more ⇒ factor = 1.25 times the old use.

Concept / Approach:
The total petrol is fixed. Duration (days) * daily use = constant. Hence new days = old days / 1.25.

Step-by-Step Solution:

Verification / Alternative check:
Let the tank contain 10 units and original daily use be 1 unit/day. After a 25% rise, daily use = 1.25 units/day. Then days = 10 / 1.25 = 8.

Why Other Options Are Wrong:
5, 6, and 7 result from over-reducing; 9 assumes too small an increase in daily use.

Common Pitfalls:
Subtracting 25% from 10 directly (to get 7.5) instead of applying inverse proportion.

Final Answer:
8