Multiple choice

The mean weight of $9$ items is $15$. If one more item is added to the series the mean becomes $16$. The value of the $10^{th}$ item is

  1. $35$
  2. $30$
  3. $25$
  4. $20$
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C Correct answer
Explanation

Sum of 9 items = 9 * 15 = 135. Sum of 10 items = 10 * 16 = 160. The 10th item = 160 - 135 = 25.

AI explanation

The sum of the first 9 items is the number of items multiplied by their mean: 9 multiplied by 15 equals 135. When the 10th item is added, the new sum becomes 10 multiplied by 16, which equals 160. The value of the 10th item is the new sum minus the old sum: 160 minus 135 equals 25.

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