Find the average of the first 18 multiples of 9.
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 85.5.
Average of first n multiples of a number = (First multiple + Last multiple) / 2
First multiple of 9 = 9 × 1 = 9
Last multiple (18th multiple) of 9 = 9 × 18 = 162
Average = (9 + 162) / 2
⇒ Average = 171 / 2
⇒ Average = 85.5