The average of all the odd integers between 2 an 22 is ?

Solution(By Examveda Team)

Series → 3 + 5 + 7 . . . . . 21
Total numbers
$$\frac{{{\text{Last term }} - {\text{ First term}}}}{{{\text{Difference}}}}$$     + 1
= $$\frac{21 - 3}{2}$$ + 1
= $$\frac{18}{2}$$ + 1
= 10
Sum of series
$$\eqalign{ & = \frac{n}{2}\left[ {2a + \left( {n - 1} \right)d} \right] \cr & = \frac{{10}}{2}\left[ {2 \times 3 + \left( {10 - 1} \right) \times 2} \right] \cr & = 5\left[ {6 + 9 \times 2} \right] \cr & = 5 \times 24 \cr & = 120 \cr} $$
Average = $$\frac{120}{10}$$ = 12