Multiple choice

The average of 25 results is 20.The average of first 12 results is 15 and that of the last 12 results is 18. Then find the 13th result?

  1. 104

  2. 159

  3. 123

  4. 147

  5. 1147
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A Correct answer
Explanation

Total sum = 25 * 20 = 500. Sum of first 12 = 12 * 15 = 180. Sum of last 12 = 12 * 18 = 216. 13th result = 500 - (180 + 216) = 500 - 396 = 104.

AI explanation

The total sum of all 25 results is 25 multiplied by 20, giving 500. The sum of the first 12 results is 12 multiplied by 15, yielding 180, and the sum of the last 12 results is 12 multiplied by 18, yielding 216. The combined sum of these 24 results is 396. The 13th result is 500 minus 396, which equals 104.

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