Product relation between HCF and LCM: For the two integers 18 and 15, compute the product HCF × LCM.
Aptitude
Problems on H.C.F and L.C.M
Difficulty: Easy
Choose an option
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A120
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B150
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C175
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D270
Answer
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