The average of the first 7 multiples of 3 is:

Correct option is B

Given:

We need to find the average of the first 7 multiples of 3.

Formula Used:

​$$\text{Average} = \frac{\text{Sum of terms}}{\text{Number of terms}}$$  

Solution: 

= 3, 6, 9, 12, 15, 18, 21 

= $$\frac{3+6+9+12+15+18+21}7$$ 

= $$\frac{84}7$$ 

= 12