Multiple choice

The mean of 7 observations is 10 and that of 3 observations is 5. What is the mean of all the 10 observations?

  1. 15

  2. 10

  3. 8.5

  4. 7.5
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C Correct answer
Explanation

Sum of 7 observations = 7 * 10 = 70. Sum of 3 observations = 3 * 5 = 15. Total sum = 85. Mean = 85 / 10 = 8.5.

AI explanation

The sum of the first 7 observations is 7 multiplied by 10, which equals 70. The sum of the remaining 3 observations is 3 multiplied by 5, which equals 15. The combined mean is the total sum divided by the total number of observations: (70 + 15) divided by 10 equals 85 divided by 10, resulting in a mean of 8.5.

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