Multiple choice

The average of 15 numbers is 26.2. If the average of first 8 numbers is 27.875 and the average of last 8 numbers is 25.125, then find the 8th number.

  1. 31

  2. 28

  3. 23

  4. 29

  5. 27
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A Correct answer
Explanation

Average of 15 numbers = 26.2

Then, sum of all 15 numbers = 26.2 * 15

= 393 

Now, average of first 8 numbers = 27.875 

So, sum of first 8 numbers = 27.875 * 8

= 223

And average of last 8 numbers = 25.125 

Then, sum of last 8 numbers = 25.125 * 8

= 201 

So, 8th number = 203 + 201 - 393

= 424 - 393

= 31

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