Find the true discount from banker’s gain and present worth: The present worth of a sum due sometime hence is ₹576 and the banker’s gain is ₹9. Determine the true discount.

Difficulty: Easy

Correct Answer: ₹ 72

Explanation:

Introduction / Context:Banker’s Gain (BG) links to True Discount (TD) and r t via BG = TD * r t = PW * (r t)^2. Given PW and BG, we can find r t and then compute TD = PW * r t.

Given Data / Assumptions:

  • PW = ₹576
  • BG = ₹9

Concept / Approach:Use:

BG = PW * (r t)^2 TD = PW * r t

Step-by-Step Solution:

Let x = r t. Then 9 = 576 * x^2 ⇒ x^2 = 9/576 = 1/64 ⇒ x = 1/8 TD = PW * x = 576 * (1/8) = ₹72

Verification / Alternative check:Since TD = PW * x = 72, BG should be TD * x = 72 * (1/8) = 9 (matches).

Why Other Options Are Wrong:Other numbers do not satisfy the squared relation between BG, PW and x = r t.

Common Pitfalls:Taking x as 9/576 instead of its square root, or mixing BD with BG/TD relations.

Final Answer:₹ 72

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