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      Question

      Aman is forming pairs of two natural numbers, A and B,

      such that their product equals 350. He wants to determine how many such pairs exist where A and B are co-prime. How many such pairs can be created? ย 
      A 5 Correct Answer Incorrect Answer
      B 6 Correct Answer Incorrect Answer
      C 2 Correct Answer Incorrect Answer
      D 4 Correct Answer Incorrect Answer

      Solution

      Co-prime numbers are the ones whose HCF is 1. The possible number of pairs of โ€˜Aโ€™ and โ€˜Bโ€™, such that, โ€˜Aโ€™ and โ€˜Bโ€™ are co-prime = 2k โ€“ 1 Where, โ€˜kโ€™ is the number of prime factors of the product. 350 = 21ย ร— 52ย ร— 71 So, the number of prime factors of 350 = k = 3 So, the possible number of pairs of โ€˜Aโ€™ and โ€˜Bโ€™, such that they are co-prime = 23 โ€“ 1ย = 22ย = 4

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