Multiple choice

If the mean of 10 numbers is 15 and that of another 20 numbers is 24, then what will be the mean of all 30 observations?

  1. 21

  2. 63

  3. 33

  4. 11

  5. None of these
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A Correct answer
Explanation

Total sum = (10 * 15) + (20 * 24) = 150 + 480 = 630. Total observations = 30. Mean = 630 / 30 = 21.

AI explanation

Using the combined mean formula, we calculate the sum of the first group as 10 multiplied by 15 to get 150, and the sum of the second group as 20 multiplied by 24 to get 480. The combined mean equals the total sum divided by the total number of observations, which is (150 + 480) divided by 30. This simplifies to 630 divided by 30, resulting in a mean of 21.

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