Multiple choice

The HCF and the LCM of two numbers are 18 and 900 respectively. How many possibilities exist for the two numbers?

  1. 3

  2. 1

  3. 2

  4. 0
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let numbers be 18a and 18b with a,b coprime. LCM = 18ab = 900, so ab = 50. The coprime pairs with product 50 are (1,50) and (2,25). This gives 2 unordered pairs: {18,900} and {36,450}.

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