The average of 11 numbers is 7.5. What should be the 12th number added to them to make the average 8.5?
Show answer & explanation
Correct answer: D
Explanation
The Correct answer is Option 4 i.e. 19.5.
We know that,
Average = Sum of observations/Number of observations
So,
The sum of 11 numbers = 7.5 × 11 = 82.5
The 12th number added to them to make the average 8.5
The sum of the 12 numbers = 8.5 × 12 = 102
Hence,
The 12th number is 102 - 82.5 = 19.5