Multiple choice

The average of 28 numbers is 77. The average of first 14 numbers is 74 and the average of last 15 numbers is 84. If the 14th number is excluded, then what is the average of remaining numbers? (correct to one decimal places)

  1. 74.7

  2. 75.7

  3. 78.7

  4. 70.7
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A Correct answer
Explanation

Total sum = 28 × 77 = 2156. Sum of first 14 = 14 × 74 = 1036. Sum of last 15 = 15 × 84 = 1260. Note: The 14th number is counted in both sums. So 1036 + 1260 = 2156 + 14th number. Therefore, 14th number = 2296 - 2156 = 140. New total = 2156 - 140 = 2016. New average = 2016 ÷ 27 = 74.67 ≈ 74.7.

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