Multiple choice

The average of 11 numbers is 63. If the average of first six numbers is 60 and the average of the last six numbers is 65, then the 6th number is-

  1. 57

  2. 60

  3. 62

  4. 64
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A Correct answer
Explanation

Sum of all 11 numbers = 11 × 63 = 693. Sum of first 6 numbers = 6 × 60 = 360. Sum of last 6 numbers = 6 × 65 = 390. The 6th number is counted in both groups, so: (sum of first 6) + (sum of last 6) - (6th number) = sum of all 11. Therefore: 360 + 390 - x = 693, so x = 750 - 693 = 57.

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