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The average of 30 results is 20 and the average of the other 20 results is 30. What is the average of all the results?

1. 24
2. 48
3. 25
4. 50

Correct answer: 24

Solution

The sum of the first 30 results is 30 × 20 = 600, and the sum of the other 20 results is 20 × 30 = 600. So the total sum is 1200 for 50 results, giving an average of 1200/50 = 24.

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