Multiple choice

If the mean of $10$ observations is $20$ and that of another $15$ observations is $16$, then the mean of $25$ observations is __________.

  1. $18$
  2. $18.2$
  3. $17.6$
  4. $17$
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C Correct answer
Explanation

Total sum = (10 * 20) + (15 * 16) = 200 + 240 = 440. Mean = 440 / 25 = 17.6.

AI explanation

Using the formula for combined mean, the sum of the first group is 10 multiplied by 20, which equals 200. The sum of the second group is 15 multiplied by 16, which equals 240. The combined mean is the total sum divided by the total number of observations, giving 200 plus 240 divided by 20 plus 15. This results in 440 divided by 25, which equals 17.6.

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