If the average of the first 15 multiples of 9 is x, then x is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 72.
First 15 multiples of 9: 9, 18, 27, ..., 135
Sum = (15/2) × (9 + 135)
⇒ 7.5 × 144 = 1080
Average = 1080 / 15 = 72
x = 72