Option 2 : 21%

**Given:**

The price of petrol increases by x%

Consumption decreases by x%

Total expenditure decreases by 16%

**Concept:**

Expenditure = Price × Consumption

**Solution:**

when price increase by x% and Consumption decreases by x% then total expenditure decreases by (x^{2} / 100)% by using successive percentage

⇒ (x^{2} / 100)% = 16%

⇒ x = 40

when price and consumption both increases by (x / 4)% then percentage change in expenditure

= (10 + 10 + (10 × 10) / 100)% = 21%

∴ required percentage = 21%