Correct Answer - Option 1 : 3x – 12
Given:
Number of terms = 9
First 6 terms = (3, 2, 9, 5, 11, 6)
Formula Used:
Average = Sum of terms/Number of terms
Calculations:
Sum of 9 terms = 9 × x = 9x ----(1)
Sum of first 6 terms = 3 + 2 + 9 + 5 + 11 + 6
⇒ Sum of first 6 terms = 36 ----(2)
Subtracting (2) from (1), we get
Sum of last 3 terms = 9x – 36
⇒ Average of last 3 terms = (9x – 36)/3
⇒ Average of last 3 terms = 3x – 12
∴ The average of the last 3 numbers is (3x – 12).
