If the price of a commodity is decreased by 30% and its consumption is

Explanation

⇒ Let the original price of commodity be x ⇒ let the original amount consumed be y ⇒ Original expenditure = xy ⇒ Price decreased by 30% ⇒ New Price = x - 30% of x = x - 0.30x = 0.70x ⇒ Consumption increased by 30% ⇒ New amount consumed = y + 30% of y = y + 0.30y = 1.30y ⇒ New expenditure = 0.70x × 1.30y ⇒ New expenditure = 0.91xy ⇒ Percentage change = [(xy - 0.91xy) / xy] × 100 ⇒ Percentage change = 0.09 × 100 ∴ Percentage change = 9% decrease