Multiple choice

The average of 11 observation is 60 if the average of first five observation is 58 and that of the last five is 56, then the sixth observation is ?

  1. 85

  2. 110

  3. 90

  4. 100
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total sum = 11 * 60 = 660. Sum of first 5 = 5 * 58 = 290. Sum of last 5 = 5 * 56 = 280. Sixth observation = 660 - (290 + 280) = 660 - 570 = 90.

AI explanation

Using the average formula, the total sum of all 11 observations is 60 multiplied by 11, which equals 660. The sum of the first five is 58 multiplied by 5 to give 290, and the sum of the last five is 56 multiplied by 5 to give 280. The sixth observation is the total sum of 660 minus the combined other sums of 570, resulting in 90.

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