If the average of the following six observations x + 2, x + 5, x + 8, x + 11, x + 14 and x+17 is 12.5, what is the average of the first three observations?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 8.
Numbers are, x + 2, x + 5, x + 8, x + 11, x + 14 and x + 17
Average = 12.5
Average = Sum of elements/Number of elements
According to the question -
x + 2 + x + 5 + x + 8 + x + 11 + x + 14 + x + 17 = 12.5 × 6
6x + 57 = 75
6x = 75 - 57
6x = 18
x = 18/6 = 3
First, three observations are 5, 8, and 11.
Sum of first three observation = 5 + 8 + 11 = 24
Average = 24/3 = 8