Multiple choice

The average of $25$ result is $18$.The average of ${1}^{st} \ 12$ is $14$ and that of last $12$ is $17$.Find the ${13}^{th}$ result.

  1. $75$
  2. $76$
  3. $77$
  4. $78$
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D Correct answer
Explanation

Sum of 25 results = 25 * 18 = 450. Sum of first 12 = 12 * 14 = 168. Sum of last 12 = 12 * 17 = 204. 13th result = 450 - (168 + 204) = 450 - 372 = 78.

AI explanation

The total sum of all 25 results is 25 multiplied by 18, which equals 450. The sum of the first 12 results is 12 multiplied by 14, or 168, and the sum of the last 12 results is 12 multiplied by 17, or 204. The 13th result is the total sum minus the sum of these 24 results, so 450 minus 168 minus 204 gives 78.

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