If the mean of the first n natural numbers is 15, what is the value of n? (2019)

Practice Questions

Q1
If the mean of the first n natural numbers is 15, what is the value of n? (2019)
  1. 29
  2. 30
  3. 31
  4. 32

Questions & Step-by-Step Solutions

If the mean of the first n natural numbers is 15, what is the value of n? (2019)
  • Step 1: Understand that the first n natural numbers are 1, 2, 3, ..., n.
  • Step 2: The formula for the mean (average) of these numbers is: Mean = (Sum of numbers) / (Total numbers).
  • Step 3: The sum of the first n natural numbers is given by the formula: Sum = n(n + 1) / 2.
  • Step 4: The total number of natural numbers is n.
  • Step 5: So, the mean can be expressed as: Mean = (n(n + 1) / 2) / n.
  • Step 6: Simplify this to: Mean = (n + 1) / 2.
  • Step 7: We know from the question that the mean is 15, so we set up the equation: (n + 1) / 2 = 15.
  • Step 8: To eliminate the fraction, multiply both sides of the equation by 2: n + 1 = 30.
  • Step 9: Now, solve for n by subtracting 1 from both sides: n = 30 - 1.
  • Step 10: Therefore, n = 29.
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