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The average of five numbers is 7. When three new numbers are included, the average of the eight numbers becomes 8.5. The average of the three new numbers is:

1. 9
2. 10.5
3. 11
4. 11.5

Correct answer: 11

Solution

Sum of the first five numbers = 5 × 7 = 35. Sum of all eight numbers = 8 × 8.5 = 68. So, sum of the three new numbers = 68 − 35 = 33, and their average = 33 ÷ 3 = 11.

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