Difficulty: Medium
Correct Answer: 640
Explanation:
Introduction / Context:When product and HCF are known, we can parameterize the two numbers as multiples of the HCF with co-prime multipliers. This approach lets us enumerate all valid unordered pairs and then compute the requested sum over distinct values appearing in those pairs.
Given Data / Assumptions:
Concept / Approach:Let a = 16x and b = 16y with HCF(x, y) = 1. Then 256xy = 7168 ⇒ xy = 7168 / 256. Factor the right-hand side, and list the coprime factor pairs (x, y). Each gives a valid unordered pair (a, b). Finally, add all distinct numbers obtained from these pairs.
Step-by-Step Solution:
Compute xy: 7168 / 256 = 28.Coprime factor pairs of 28: (1, 28) and (4, 7). (2, 14) is not coprime.Corresponding (a, b) pairs: (16*1, 16*28) = (16, 448) and (16*4, 16*7) = (64, 112). Orders reversed are the same unordered pairs.Distinct numbers appearing: 16, 448, 64, 112. Sum = 16 + 448 + 64 + 112 = 640.Verification / Alternative check:
Check HCFs: HCF(16, 448) = 16; HCF(64, 112) = 16. Products: 16*448 = 7168 and 64*112 = 7168, both correct.Why Other Options Are Wrong:
Common Pitfalls:
Final Answer:
640
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