Find the average of the first 18 multiples of 9.
- A88.5
- B82.3
- C85.5
- D84.6
Solution & Step-by-step Explanation
The first 18 multiples of 9 form an Arithmetic Progression (AP):
9,18,27,…,(9×18)
First term (a)=9
Last term (l)=9×18=162
The average of any terms in an Arithmetic Progression is given by the formula:
Average=
2
First term+Last term
Average=
2
9+162
=
2
171
=85.5
9,18,27,…,(9×18)
First term (a)=9
Last term (l)=9×18=162
The average of any terms in an Arithmetic Progression is given by the formula:
Average=
2
First term+Last term
Average=
2
9+162
=
2
171
=85.5