Product relation between HCF and LCM: For the two integers 18 and 15, compute the product HCF × LCM.

Difficulty: Easy

Correct Answer: 270

Explanation:

Introduction / Context:For any two positive integers a and b, the fundamental identity holds: HCF(a, b) * LCM(a, b) = a * b. This allows quick computation of one product given the numbers themselves.

Given Data / Assumptions:

  • a = 18, b = 15
  • We want HCF * LCM for this pair.

Concept / Approach:Use the identity directly: the product of HCF and LCM equals the product of the two numbers. There is no need to compute HCF and LCM separately in this case.

Step-by-Step Solution:

Compute a * b = 18 * 15 = 270.Therefore HCF(18,15) * LCM(18,15) = 270.

Verification / Alternative check:

Indeed, HCF(18,15) = 3 and LCM(18,15) = 90, and 3 * 90 = 270, confirming the identity.

Why Other Options Are Wrong:

  • 120, 150, 175 do not equal 18 * 15 and thus contradict the fundamental relation.

Common Pitfalls:

  • Mistakenly adding HCF and LCM or computing them separately with errors.

Final Answer:

270

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