The price of wheat flour rises by 50%. By what percentage must a family reduce its consumption so that its spending on wheat flour stays the same?

💡 Solution & Explanation

Spending = price × quantity. Take the old price as 100 and the old quantity as 100, so the spending is 10,000. The new price is 150, so the quantity must become 10,000 ÷ 150 = 66.67. That is a cut of 33.33%. Shortcut: reduction % = rise ÷ (100 + rise) × 100 = 50 ÷ 150 × 100. Cutting by 50% would leave the family spending less than before.