Maintaining a price ratio after changes: Prices of two articles are in the ratio 3 : 4. If the first increases by 10% and the second increases by ₹4 so that the original ratio remains 3 : 4, find the original price of the second article.

Difficulty: Medium

Correct Answer: ₹ 40

Explanation:


Introduction / Context:
This is a ratio preservation problem with a percentage change on one item and an absolute change on the other. We set unknowns for original prices, apply changes, and force the ratio to remain 3 : 4, then solve for the scale factor.

Given Data / Assumptions:

  • Original prices: First = 3x, Second = 4x.
  • Change: First increases by 10% ⇒ 3x becomes 3.3x.
  • Change: Second increases by ₹4 ⇒ 4x becomes 4x + 4.
  • Post-change ratio remains 3 : 4.


Concept / Approach:
Impose 3.3x : (4x + 4) = 3 : 4. Cross-multiply to get a linear equation in x and solve. The second’s original price is 4x.


Step-by-Step Solution:

3.3x / (4x + 4) = 3/44 * 3.3x = 3 * (4x + 4)13.2x = 12x + 12 ⇒ 1.2x = 12 ⇒ x = 10Original second price = 4x = ₹40.


Verification / Alternative check:
New prices: First = 33, Second = 44. Ratio 33 : 44 simplifies to 3 : 4, matching the condition.


Why Other Options Are Wrong:

  • ₹10, ₹30, ₹35: Do not satisfy the preserved ratio when tested with the given changes.


Common Pitfalls:
Applying 10% to the ratio instead of the first price, or forgetting that ₹4 is an absolute change, not percentage-based.


Final Answer:

₹ 40

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