Average of 30 observations is 60. Average of first 15 observations is 62. Average of last 16 observations is 55. What is the value of 15th observation?
Show answer & explanation
Correct answer: C
Explanation
Given:
Total observations = 30, Average = 60
Average of the first 15 = 62
Average of the last 16 = 55
Total sum = 30 × 60 = 1800
Sum of the first 15 = 15 × 62 = 930
Sum of the last 16 = 16 × 55 = 880
The 15th observation is common to both sets.
15th observation = 930 + 880 − 1800 = 10