Multiple choice

If the mean of a set of $15$ observations is $12$ and that of another set of $10$ observations is $15$ then find the mean of combined set.

  1. $15$
  2. $14.1$
  3. $12.5$
  4. $13.2$
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D Correct answer
Explanation

The total sum of the first set is 15 * 12 = 180. The total sum of the second set is 10 * 15 = 150. The combined mean is (180 + 150) / (15 + 10) = 330 / 25 = 13.2.

AI explanation

Using the combined mean formula, the sum of the first set is 15 multiplied by 12, which is 180, and the sum of the second set is 10 multiplied by 15, which is 150. The combined mean is (180 + 150) divided by (15 + 10), resulting in 330 divided by 25. This calculation gives a combined mean of 13.2.

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