The average of 15 results is 60. If the average of the first eight results is 58, and that of the last six is 62, then find the ninth result.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is Option 3 i.e. 64.
We know that,
Average = Sum of observations/Number of observations
We are given that the average of 15 results is 60
Sum of all results = 60 × 15 = 900
We are also given that the average of the first eight results is 58
The sum of the first eight results = 58 × 8 = 464
Similarly, the average of the last six results is 62
The sum of the last six results = 62 × 6 = 372
Ninth result = Sum of all results - Sum of the first eight results - Sum of the last six results
Ninth result = 900 - 464 - 372 = 64
Therefore, the ninth result is 64