More Questions from Number System

The sum of squares of two numbers is 68, and the square of their difference is 36. Find the product of the two numbers.

Aptitude Number System Difficulty: Easy
Choose an option
  • A
    16
  • B
    32
  • C
    58
  • D
    104
  • E
    22

Answer

Correct Answer: 16

Explanation

Introduction / Context:This question leverages the identity for the square of a difference and its relationship to the product term. With aggregate information (sum of squares and squared difference), we can deduce the product directly without solving for individual numbers.

Given Data / Assumptions:

  • a^2 + b^2 = 68.
  • (a − b)^2 = 36.
  • We need ab.

Concept / Approach:Use the identity (a − b)^2 = a^2 + b^2 − 2ab. Plug in the given values and solve for ab. This bypasses solving a quadratic for a and b and goes straight to the required product.

Step-by-Step Solution:

Start: (a − b)^2 = a^2 + b^2 − 2ab.Substitute: 36 = 68 − 2ab.Rearrange: 2ab = 68 − 36 = 32.Therefore, ab = 32 / 2 = 16.

Verification / Alternative check:Optional: (a + b)^2 = a^2 + b^2 + 2ab = 68 + 32 = 100 → a + b = 10 is consistent with real solutions (e.g., numbers satisfying sum 10 and product 16 exist).

Why Other Options Are Wrong:32 represents 2ab, not ab. 58 and 104 are inconsistent with the identity. 22 is arbitrary here.

Common Pitfalls:Forgetting to divide by 2 after finding 2ab, or mixing identities for (a − b)^2 and (a + b)^2.

Final Answer:16

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