Multiple choice

The numbers $4$ and $9$ have frequencies $x$ and $(x-1)$ respectively If their arithmetic mean is $6$ then $x$ is equal to

  1. $2$
  2. $3$
  3. $4$
  4. $5$
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B Correct answer
Explanation

Mean = (4x + 9(x-1)) / (x + x-1) = 6. (4x + 9x - 9) / (2x - 1) = 6. 13x - 9 = 12x - 6. x = 3.

AI explanation

The arithmetic mean formula gives (4*x + 9*(x-1)) divided by (x + x - 1) = 6. This simplifies to (13x - 9) divided by (2x - 1) = 6. Cross-multiplying yields 13x - 9 = 12x - 6, which gives x = 3.

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