The average of 28 numbers is 77. The average of first 14 numbers is 74 and the average of last 15 numbers is 84. If the 14th number is excluded, then what is the average of remaining numbers? (correct to one decimal places)
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 74.7
Sum of all observations = number of observations × average
⇒ 77 × 28 = 2156
Sum of first 14 numbers = 14 × 74
⇒ 1036
Sum of 14th term to 28th term = 15 × 84
⇒ 1260
Sum of all the numbers including the 14th number twice = 1036 + 1260
⇒ 2296
14th number = 2296 - 2156
⇒ 140
When the 14th number is not included: 2156 - 140
⇒ 2016
Average = 2016/27
⇒ 74.67 or 74.7