Solutions
Given:
a1, a2, ..., a8 are eight numbers whose average = 40
Average of numbers at even places = 25
Formula used:
Average = (Sum of terms)/(Number of terms)
Calculation:
The sum of these eight numbers = 8 × 40 = 320
The average of the numbers at even places (a2, a4, a6, a8) = 25.
The sum of these four numbers = 4 × 25 = 100
Now, we subtract the sum of the numbers at even places from the total sum, and then divide by the number of odd places.
The sum of the numbers at odd places = 320 - 100 = 220
There are 4 numbers at odd places, their average is 220/4 = 55
∴ Average of numbers at odd places is 55.