Math Problem Statement

The owner of a shop increases the price of an article by x% and then decreases it by x%. As a result, the price of the article falls by Rs. 180. After one more such iteration, the price falls by a further Rs. 160. Find the original price (in rupees) of the article.

Solution

Let's solve this problem step by step.

Problem Breakdown:

  • The price of the article increases by x%x\% and then decreases by x%x\%, leading to a drop in price by Rs. 180.
  • After one more iteration (increase by x%x\% and then decrease by x%x\%), the price falls further by Rs. 160.
  • We need to find the original price of the article.

Key Concept:

When the price is increased by x%x\% and then decreased by x%x\%, the net effect on the price is a decrease, as the percentage decrease applies to the increased price. The formula for the new price after an increase and then decrease of x%x\% is: New Price=P×(1x21002)\text{New Price} = P \times \left(1 - \frac{x^2}{100^2}\right) where PP is the price before the operation.

Let the original price be P0P_0, and the change factor be: k=(1x21002)k = \left(1 - \frac{x^2}{100^2}\right) After the first iteration: P1=P0×kP_1 = P_0 \times k The difference after the first iteration is: P0P1=180P0P0×k=180P0(1k)=180P_0 - P_1 = 180 \quad \Rightarrow \quad P_0 - P_0 \times k = 180 \quad \Rightarrow \quad P_0 (1 - k) = 180

After the second iteration: P2=P1×k=P0×k2P_2 = P_1 \times k = P_0 \times k^2 The difference after the second iteration is: P1P2=160P0×kP0×k2=160P0k(1k)=160P_1 - P_2 = 160 \quad \Rightarrow \quad P_0 \times k - P_0 \times k^2 = 160 \quad \Rightarrow \quad P_0 k (1 - k) = 160

System of Equations:

We now have two equations:

  1. P0(1k)=180P_0 (1 - k) = 180
  2. P0k(1k)=160P_0 k (1 - k) = 160

We can solve these two equations simultaneously to find P0P_0 (the original price) and kk. Let's solve this now.The solution to the system of equations gives us the original price of the article, P0=1620P_0 = 1620 rupees, and the change factor k=89k = \frac{8}{9}.

Thus, the original price of the article is Rs. 1620.

Would you like more details or have any further questions? Here are 5 related questions for practice:

  1. How does the percentage increase and decrease lead to an overall price drop?
  2. What is the impact on the final price if the increase and decrease percentages are different?
  3. If the owner repeated this process three times, what would be the price reduction?
  4. Can you find the percentage x%x\% that caused the drop in price?
  5. What is the total percentage drop in price after two iterations?

Tip: When prices are increased and then decreased by the same percentage, the overall effect is always a decrease. The percentage loss is quadratic, not linear.

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Math Problem Analysis

Mathematical Concepts

Algebra
Simultaneous Equations
Percentage Increase and Decrease

Formulas

New Price = P × (1 - x² / 100²)
P₀(1 - k) = 180
P₀k(1 - k) = 160

Theorems

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Suitable Grade Level

Grade 10-12